Month to Century Converter
Convert months to centuries with our free online time converter.
Quick Answer
1 Month = 0.000833 centuries
Formula: Month × conversion factor = Century
Use the calculator below for instant, accurate conversions.
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All conversion formulas on UnitsConverter.io have been verified against NIST (National Institute of Standards and Technology) guidelines and international SI standards. Our calculations are accurate to 10 decimal places for standard conversions and use arbitrary precision arithmetic for astronomical units.
Month to Century Calculator
How to Use the Month to Century Calculator:
- Enter the value you want to convert in the 'From' field (Month).
- The converted value in Century will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Time category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Month to Century: Step-by-Step Guide
Converting Month to Century involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
1 Month = 0.000833333 centuriesExample Calculation:
Convert 60 months: 60 × 0.000833333 = 0.05 centuries
Disclaimer: For Reference Only
These conversion results are provided for informational purposes only. While we strive for accuracy, we make no guarantees regarding the precision of these results, especially for conversions involving extremely large or small numbers which may be subject to the inherent limitations of standard computer floating-point arithmetic.
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Need to convert to other time units?
View all Time conversions →What is a Month and a Century?
A month is a unit of time used with calendars, approximately based on the orbital period of the Moon around Earth. The word "month" derives from "Moon" (Proto-Germanic mǣnōth).
Modern Gregorian Calendar Months
In the Gregorian calendar (standard worldwide since 1582), months have irregular lengths:
| Month | Days | Hours | Weeks (approx) | |-----------|----------|-----------|-------------------| | January | 31 | 744 | 4.43 | | February | 28 (29 leap) | 672 (696 leap) | 4.00 (4.14 leap) | | March | 31 | 744 | 4.43 | | April | 30 | 720 | 4.29 | | May | 31 | 744 | 4.43 | | June | 30 | 720 | 4.29 | | July | 31 | 744 | 4.43 | | August | 31 | 744 | 4.43 | | September | 30 | 720 | 4.29 | | October | 31 | 744 | 4.43 | | November | 30 | 720 | 4.29 | | December | 31 | 744 | 4.43 |
Average Month for Conversions
For mathematical conversions, an average month is defined as:
- 1/12th of a year = 365.25 days ÷ 12 = 30.4375 days (often rounded to 30.44 days)
- 730.5 hours (30.4375 × 24)
- 43,830 minutes (730.5 × 60)
- 2,629,800 seconds (43,830 × 60)
- 4.35 weeks (30.4375 ÷ 7)
Lunar Month vs. Calendar Month
- Synodic month (lunar cycle, new moon to new moon): 29.53 days (29 days, 12 hours, 44 minutes, 3 seconds)
- Sidereal month (Moon's orbit relative to stars): 27.32 days
- Gregorian calendar month: 28-31 days (avg 30.44 days)
- Drift: Calendar months drift ~2 days per month from lunar phases
A century is a unit of time equal to 100 consecutive years. The word derives from Latin "centum" (one hundred).
Duration in Other Units
1 century equals:
- 100 years (exactly)
- 10 decades (100 ÷ 10)
- 1,200 months (100 × 12)
- ~5,217 weeks (100 × 52.17)
- 36,524 days (100 common years) or 36,525 days (accounting for ~25 leap years)
- Average: 36,525 days (100 × 365.25)
- 876,600 hours (36,525 × 24)
- 52,596,000 minutes (876,600 × 60)
- 3,155,760,000 seconds (52,596,000 × 60)
Century Boundaries: The 1 vs. 0 Debate
Formal reckoning (technically correct):
- 1st century: 1-100 CE
- 18th century: 1701-1800
- 19th century: 1801-1900
- 20th century: 1901-2000
- 21st century: 2001-2100
Why? Because there was no year 0 in the Gregorian calendar (1 BCE → 1 CE directly), the first century was years 1-100, not 0-99.
Popular usage (dominant in practice):
- 18th century: "The 1700s" (1700-1799)
- 19th century: "The 1800s" (1800-1899)
- 20th century: "The 1900s" (1900-1999)
- 21st century: "The 2000s onward" (2000-2099)
Reality: Popular usage dominates. When people say "20th century," they typically mean 1900-1999, not 1901-2000. The millennium celebration happened January 1, 2000, not January 1, 2001, despite formal correctness.
Note: The Month is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Century belongs to the imperial/US customary system.
History of the Month and Century
of the Month
1. Ancient Lunar Origins (Pre-3000 BCE)
The concept of the month originated from observing the lunar cycle—the period from one new moon to the next, approximately 29.53 days (synodic month).
Early lunar calendars:
- Babylonian calendar (c. 2000 BCE): 12 lunar months (~354 days per year), with periodic intercalary (13th) months added every 2-3 years to realign with seasons
- Egyptian calendar (c. 3000 BCE): 12 months of exactly 30 days each (360 days) + 5 epagomenal days = 365 days, detached from lunar cycle
- Hebrew/Jewish calendar (c. 1500 BCE): Lunisolar calendar with 12-13 months (29-30 days each), still used today for religious observances
- Chinese calendar (c. 1600 BCE): Lunisolar calendar with 12-13 months, determining Chinese New Year (late January to mid-February)
Why lunar months? Ancient civilizations without artificial lighting noticed the Moon's dramatic visual changes every ~29.5 days, making it an obvious natural timekeeper.
2. Roman Calendar Evolution (753 BCE - 46 BCE)
The Roman calendar underwent dramatic transformations:
Romulus Calendar (753 BCE - legendary):
- 10 months, 304 days total, starting in March (spring equinox)
- Months: Martius (31), Aprilis (30), Maius (31), Junius (30), Quintilis (31), Sextilis (30), September (30), October (31), November (30), December (30)
- Winter gap (~61 days) was unnamed, creating calendar chaos
Numa Pompilius Reform (c. 713 BCE):
- Added January and February to fill winter gap
- 12 months, 355 days total (still 10.25 days short of solar year)
- Required periodic intercalary months (Mercedonius) to realign with seasons
- Romans disliked even numbers, so most months had 29 or 31 days (February got unlucky 28)
Late Roman Republic (c. 100 BCE):
- Calendar administration corrupt—priests (pontifices) manipulated intercalary months for political gain (extending terms, delaying elections)
- Calendar drifted months out of sync with seasons (harvest festivals in wrong seasons)
3. Julian Calendar (46 BCE - 1582 CE)
Julius Caesar's reform (46 BCE):
- Consulted Egyptian astronomer Sosigenes of Alexandria
- Adopted solar year = 365.25 days (365 days + leap day every 4 years)
- Redesigned month lengths to solar-based 28-31 days:
- 31 days: January, March, May, July (Quintilis), September, November
- 30 days: April, June, August (Sextilis), October, December
- 28/29 days: February (unlucky month, kept short)
- 46 BCE = "Year of Confusion" (445 days long to realign calendar with seasons)
Later adjustments:
- 44 BCE: Quintilis renamed July (Julius Caesar, after his assassination)
- 8 BCE: Sextilis renamed August (Augustus Caesar)
- August given 31 days (stealing 1 from February) to match July's prestige, redistributing others
- Final pattern: Jan(31), Feb(28/29), Mar(31), Apr(30), May(31), Jun(30), Jul(31), Aug(31), Sep(30), Oct(31), Nov(30), Dec(31)
Problem with Julian calendar: Solar year = 365.2422 days (not exactly 365.25), so calendar gained ~11 minutes per year = 3 days every 400 years
4. Gregorian Calendar (1582 CE - Present)
Pope Gregory XIII's reform (1582):
- Corrected drift: Removed 10 days (October 4, 1582 → October 15, 1582) to realign with seasons
- New leap year rule:
- Leap year every 4 years (like Julian)
- EXCEPT century years (1700, 1800, 1900) NOT leap years
- EXCEPT century years divisible by 400 (1600, 2000, 2400) ARE leap years
- Result: 97 leap years per 400 years = 365.2425 days average (only 27 seconds/year error)
- Month lengths unchanged from final Julian pattern
Adoption:
- Catholic countries (Spain, Portugal, Italy): Immediately (1582)
- Protestant countries (Britain, colonies): 1752 (removed 11 days: Sept 2 → Sept 14)
- Russia: 1918 (removed 13 days, after October Revolution became November Revolution)
- China: 1912 (Republic of China adoption)
- Turkey: 1926 (secular reforms)
- Now universal for civil purposes worldwide
5. Lunar Calendars Continue
Despite Gregorian dominance, lunar/lunisolar calendars continue for religious/cultural purposes:
- Islamic Hijri calendar: 12 lunar months (354-355 days), cycles through seasons every 33 years, determines Ramadan
- Hebrew calendar: Lunisolar with 12-13 months, determines Jewish holidays
- Chinese calendar: Lunisolar, determines Chinese New Year, Mid-Autumn Festival
- Hindu calendars: Multiple regional lunisolar systems
- Buddhist calendars: Various lunisolar systems across Thailand, Sri Lanka, Myanmar
of the Century Concept
1. Ancient Origins: Roman Centuria (509 BCE - 27 BCE)
Roman military organization:
- Centuria (plural: centuriae) = Roman military unit of approximately 100 soldiers (later reduced to 80)
- Led by a centurion (centurio)
- Latin "centum" = one hundred
- 6 centuries = 1 cohort; 10 cohorts = 1 legion (~6,000 soldiers)
Early timekeeping:
- Romans used Ab urbe condita (AUC, "from the founding of the city") dating from Rome's legendary founding (753 BCE)
- No systematic use of "century" for 100-year periods yet
- Time organized by consulships, reigns, dynasties
2. Calendar Development and Anno Domini Dating (1 CE - 1582 CE)
Anno Domini (AD) system:
- Dionysius Exiguus (c. 525 CE): Calculated years from Jesus Christ's birth
- Introduced Anno Domini (AD, "in the year of the Lord") dating
- Critical error: No year 0 (went directly from 1 BCE to 1 CE)
- This creates century boundary confusion still debated today
Julian Calendar (46 BCE - 1582 CE):
- Julius Caesar introduced 365.25-day year (leap year every 4 years)
- Provided stable framework for long-term chronology
- Enabled systematic dating of events over centuries
Gregorian Calendar Reform (1582 CE):
- Pope Gregory XIII corrected Julian calendar drift
- Established modern calendar system still used today
- Removed 10 days (October 4, 1582 → October 15, 1582)
- Century years divisible by 400 are leap years (1600, 2000), others not (1700, 1800, 1900)
3. Renaissance and Enlightenment: Historical Periodization (1400s-1700s)
Systematic historiography emerged:
- 15th-16th centuries: Renaissance scholars developed historical chronologies
- 17th-18th centuries: Enlightenment historians systematized century-based periodization
- Edward Gibbon (Decline and Fall of the Roman Empire, 1776-1789): Used century-scale analysis
Why centuries became standard:
- Generational scale: ~4 generations per century = intergenerational change visible but comprehensible
- Administrative records: Tax records, census data, government documents accumulated over centuries
- Pattern recognition: 100-year scale reveals structural changes invisible in decade-scale analysis
- Round number psychology: Base-10 counting makes 100-year periods psychologically satisfying
Periodization labels emerged:
- "The 16th century" = 1500s Renaissance, Reformation
- "The 17th century" = 1600s Scientific Revolution, Baroque
- "The 18th century" = 1700s Age of Enlightenment, Industrial Revolution begins
4. 19th Century: Century as Historical Framework (1801-1900)
The "long 19th century" concept:
- Historians sometimes define as 1789-1914 (French Revolution to WWI)
- Captures coherent historical era despite not matching formal century boundaries
Major 19th-century transformations:
- Industrial Revolution (1760-1840): Steam power, factories, railroads
- Urbanization: Rural → urban population shift
- Imperialism: European colonial empires peak
- Scientific progress: Darwin, Maxwell, Mendel
- Political revolutions: 1848 Revolutions, unification of Germany/Italy
- Technological: Telegraph, telephone, photography, electricity
Century consciousness:
- People in 1800s increasingly thought in century-scale terms
- "The spirit of the 19th century" = common phrase
- Fin de siècle (end of century, 1890s-1900s) = cultural movement
5. 20th Century: Century of Extremes (1901-2000)
Eric Hobsbawm's "short 20th century" (1914-1991):
- WWI start to Soviet Union collapse
- Captures coherent historical narrative despite formal century boundaries
Major 20th-century transformations:
- World Wars: WWI (1914-1918), WWII (1939-1945)
- Ideological conflict: Fascism, Communism, Capitalism compete
- Cold War (1947-1991): US vs. USSR, nuclear arms race
- Decolonization: European empires disintegrate (1940s-1970s)
- Technological revolutions:
- Automobiles, airplanes (early 1900s)
- Nuclear energy (1940s)
- Computers (1940s-1950s)
- Space exploration (1950s-1960s)
- Internet (1990s)
- Mobile phones (1990s-2000s)
- Population explosion: 1.6 billion (1900) → 6.1 billion (2000)
- Medical advances: Antibiotics, vaccines, life expectancy doubled
- Environmental: Climate change, ozone depletion, biodiversity loss
Century labeling:
- "The American Century" (Henry Luce, 1941): US dominance of 20th century
- "The People's Century" (BBC, 1995): Mass politics, democracy spread
6. 21st Century: Digital Age and Beyond (2001-Present)
Millennium transition debate:
- Popular celebration: January 1, 2000 (Y2K)
- Formal start: January 1, 2001
- Most people celebrated 2000 despite pedantic correctness
21st-century defining features (so far):
- 9/11 attacks (2001): "War on Terror" begins
- Digital revolution: Smartphones ubiquitous (iPhone 2007)
- Social media: Facebook, Twitter, Instagram, TikTok
- Climate crisis: Accelerating global warming, extreme weather
- COVID-19 pandemic (2020-2023): Global disruption
- AI revolution: ChatGPT (2022), generative AI breakthroughs
- Geopolitical shifts: Rise of China, multipolar world
- Economic: 2008 Financial Crisis, wealth inequality
"21st-century skills": Digital literacy, critical thinking, adaptability
Common Uses and Applications: months vs centuries
Explore the typical applications for both Month (imperial/US) and Century (imperial/US) to understand their common contexts.
Common Uses for months
and Applications
1. Financial Planning and Budgeting
Monthly budget framework:
- Income: Track monthly take-home pay (after taxes)
- Fixed expenses: Rent/mortgage, car payment, insurance (consistent monthly amounts)
- Variable expenses: Groceries, utilities, entertainment (varies month-to-month)
- Savings goals: "Save $500/month" = $6,000/year
- Debt repayment: "Extra $200/month toward credit card" = $2,400/year payoff
Monthly vs. annual thinking:
- $150/month subscription = $1,800/year (psychological impact: monthly feels smaller)
- "Latte factor": $5 daily coffee = $150/month = $1,800/year = $18,000/decade
Monthly financial ratios:
- Rent rule: Rent should be ≤30% of monthly gross income
- 50/30/20 rule: 50% needs, 30% wants, 20% savings (monthly breakdown)
2. Subscription and Membership Economy
Monthly Recurring Revenue (MRR) = business model foundation:
- SaaS (Software as a Service): Monthly subscription pricing (e.g., Adobe Creative Cloud $54.99/month)
- Streaming services: Netflix, Spotify, Disney+ (monthly billing standard)
- Gym memberships: Monthly dues (e.g., $30-100/month depending on gym)
- Amazon Prime: $14.99/month (or $139/year = $11.58/month, annual cheaper)
Monthly vs. annual pricing psychology:
- Annual = higher upfront cost, lower monthly rate, customer lock-in
- Monthly = lower barrier to entry, higher churn risk, higher effective rate
3. Project Management and Milestones
Standard project durations:
- 1-month sprint: Agile/Scrum often uses 2-4 week sprints (close to 1 month)
- 3-month project: Standard short-term project (1 quarter)
- 6-month project: Medium-term initiative (2 quarters, half-year)
- 12-month project: Long-term strategic initiative (full year)
Monthly milestones:
- Month 1: Planning and setup
- Month 2: Development/implementation
- Month 3: Testing and refinement
- Month 4: Launch and monitoring
4. Employment and Compensation
Pay period variations:
- Monthly (12 pay periods/year): Common internationally, especially Europe/Asia
- Pros: Aligns with monthly bills, simpler accounting
- Cons: Long gap between paychecks (especially if month has 31 days)
- Semi-monthly (24 pay periods/year): 1st and 15th of each month
- Pros: More frequent pay (twice per month), aligns with mid-month expenses
- Cons: Pay dates vary (weekends/holidays), inconsistent days between paychecks
- Bi-weekly (26 pay periods/year): Every 2 weeks (e.g., every other Friday)
- Pros: Consistent day of week, 2 "extra" paychecks per year
- Cons: Doesn't align with monthly bills, some months have 3 paychecks
Monthly salary vs. hourly:
- Salaried: Annual salary ÷ 12 = monthly salary (e.g., $72,000/year = $6,000/month)
- Hourly: (Hourly rate × hours/week × 52 weeks) ÷ 12 months (e.g., $25/hr × 40hrs × 52 ÷ 12 = $4,333/month)
5. Calendar Organization
Month as primary calendar unit:
- Monthly view: Standard calendar layout (7 columns × 4-6 rows = 28-42 cells)
- Month numbering: January = 1, February = 2, ... December = 12
- Date notation:
- US: MM/DD/YYYY (month first)
- International (ISO 8601): YYYY-MM-DD (year-month-day)
- European: DD/MM/YYYY (day first)
Month-based planning:
- Goals: "Read 2 books per month" = 24 books/year
- Habits: "Exercise 3 times per week" = 12-13 times per month
- Reviews: "Monthly review" of goals, finances, habits
6. Seasonal Business Cycles
Retail calendar:
- January: Post-holiday sales, fitness equipment (New Year's resolutions)
- February: Valentine's Day
- March-April: Spring cleaning, Easter, tax season
- May: Mother's Day, Memorial Day (unofficial summer start)
- June: Father's Day, graduations, weddings
- July-August: Summer travel, back-to-school shopping (late August)
- September: Labor Day, fall season begins
- October: Halloween
- November: Thanksgiving, Black Friday (biggest shopping day)
- December: Holiday shopping season (Christmas/Hanukkah)
Quarterly thinking (3-month periods):
- Q1 (Jan-Mar): New Year momentum, tax season
- Q2 (Apr-Jun): Spring/early summer, end of fiscal year for many companies
- Q3 (Jul-Sep): Summer slowdown, back-to-school
- Q4 (Oct-Dec): Holiday season, year-end push, budget planning
7. Age and Developmental Milestones
Infant/child development:
- 0-12 months: Tracked monthly (dramatic changes each month)
- 3 months: Lifts head, smiles
- 6 months: Sits up, starts solid foods
- 9 months: Crawls, says "mama/dada"
- 12 months: Walks, first words
- 12-24 months: Often still tracked monthly ("18 months old" vs. "1.5 years")
- 2+ years: Typically switch to years ("3 years old")
Age expression:
- Months (0-23 months): More precise for developmental tracking
- Years (2+ years): Standard for most purposes
- Decades (30s, 40s, etc.): Rough life stages
When to Use centuries
and Applications
1. Historical Analysis and Research
Century-by-century comparison:
- Economic growth: "19th-century industrialization vs. 20th-century information age"
- Warfare evolution: "19th-century muskets → 20th-century machine guns → 21st-century drones"
- Life expectancy trends: Analyzed century-by-century
Academic papers:
- "This study examines voting patterns across two centuries (1800s-1900s)"
- "Century-scale climate reconstructions"
2. Art, Literature, and Cultural Studies
Periodization:
- "18th-century literature": Age of Enlightenment, Voltaire, Swift, Johnson
- "19th-century novel": Dickens, Austen, Tolstoy, Dostoevsky
- "20th-century art": Impressionism, Cubism, Surrealism, Abstract Expressionism
Art history courses: Often organized by century ("Art of the 17th Century")
3. Genealogy and Family History
Tracing ancestry:
- 4-5 generations per century = century scale ideal for family trees
- "My great-great-grandfather lived in the 19th century"
- Immigration records, census data organized by century
Life stages across centuries:
- Born late 1800s, died mid-1900s = lived through two centuries
4. Climate and Environmental Science
Century-scale climate patterns:
- Medieval Warm Period (10th-13th centuries): Warmer than average
- Little Ice Age (14th-19th centuries): Cooler than average
- 20th-21st century warming: Anthropogenic climate change
Projections:
- "By end of 21st century, sea level rise 1-2 meters"
5. Economic and Development Studies
Long-term economic trends:
- 19th century: Agricultural → industrial economies
- 20th century: Industrial → service/information economies
- 21st century: Digital/knowledge economies
Development indicators: Tracked over centuries (literacy, GDP, poverty)
6. Philosophy and Long-Term Thinking
"Think in centuries":
- Long Now Foundation: 10,000-year thinking
- Contrast with short-term thinking (quarterly earnings, election cycles)
Philosophical movements:
- 18th century: Enlightenment rationalism
- 19th century: Romanticism, existentialism emerges
- 20th century: Postmodernism
7. Legal and Property Rights
Land ownership records:
- Property deeds reference century-old transactions
- "Century farms": Farms in same family 100+ years
Copyright:
- Life + 70 years = often extends into next century after author's death
Additional Unit Information
About Month (mo)
1. How many days are in a month?
It varies by month:
- 31 days: January, March, May, July, August, October, December (7 months)
- 30 days: April, June, September, November (4 months)
- 28 days: February (non-leap year)
- 29 days: February (leap year, every 4 years with exceptions)
Average month = 30.44 days (365.25 ÷ 12), used for conversions.
Mnemonic: "30 days hath September, April, June, and November. All the rest have 31, except February alone, which has 28 days clear, and 29 in each leap year."
Knuckle trick: Make fists and count across knuckles (31 days) and valleys (30 days, except February).
2. Why do months have different lengths?
Historical reasons:
- Roman calendar origins: 10-month calendar (Romulus) had 304 days, leaving ~61-day winter gap
- Numa Pompilius added January and February (c. 713 BCE), creating 12 months with 355 days
- Julius Caesar (46 BCE): Julian calendar with 365.25-day year required distributing days across 12 months
- Political decisions: July (Julius Caesar) and August (Augustus Caesar) both given 31 days for prestige, shortening February to 28 days
Result: Irregular pattern (31-28-31-30-31-30-31-31-30-31-30-31) due to Roman politics, not astronomy.
3. What is an average month length used for conversions?
Average month = 30.4375 days (often rounded to 30.44 days)
Calculation: 365.25 days per year ÷ 12 months = 30.4375 days per month
- 365.25 accounts for leap year (365 × 3 years + 366 × 1 year = 1,461 days ÷ 4 years = 365.25)
When to use average month:
- Converting months to days/weeks/hours when specific month unknown
- Financial calculations (monthly interest rates, annual salary ÷ 12)
- Age approximations ("6 months old" ≈ 183 days)
When NOT to use average: Specific date calculations (use actual month lengths).
4. Is a month based on the Moon?
Historically, yes. Currently, only approximately.
Etymology: "Month" derives from "Moon" (Old English mōnað, Proto-Germanic mǣnōth).
Lunar cycle: 29.53 days (synodic month, new moon to new moon)
Gregorian calendar month: 28-31 days (avg 30.44 days)
- Drift: Calendar months drift ~2 days per month from lunar phases
- Example: Full moon on January 15 → next full moon ~February 13 (29.5 days later), not February 15
Modern lunar calendars:
- Islamic calendar: Strictly lunar (12 months × 29.5 days = 354 days), cycles through seasons every 33 years
- Hebrew/Chinese calendars: Lunisolar (12-13 months, adding extra month every 2-3 years to stay aligned with seasons)
Why detached? Solar year (365.24 days) and lunar year (354.37 days) are incompatible—12 lunar months = 10.87 days short of solar year.
5. How many weeks are in a month?
Average month = 4.35 weeks (30.44 days ÷ 7 days/week)
Common mistake: Assuming 1 month = 4 weeks (WRONG—actually 4 weeks = 28 days, most months are 30-31 days)
Specific months:
- 28 days (February, non-leap) = 4.00 weeks
- 29 days (February, leap) = 4.14 weeks
- 30 days (April, June, September, November) = 4.29 weeks
- 31 days (January, March, May, July, August, October, December) = 4.43 weeks
Implications:
- "4 weeks pregnant" ≠ "1 month pregnant" (4 weeks = 28 days, 1 month avg = 30.44 days)
- "Save $100/week" = $435/month (not $400)
6. How many months are in a year?
12 months in all major calendar systems (Gregorian, Julian, Hebrew, Chinese, Hindu).
Why 12 months?
- Lunar approximation: 12 lunar cycles (~354 days) close to solar year (365 days)
- Convenient division: 12 has many factors (1, 2, 3, 4, 6, 12), making quarters (3 months), half-years (6 months) easy
- Historical precedent: Babylonian, Roman calendars used 12 months
Alternative proposals (failed):
- French Republican Calendar (1793-1805): 12 months × 30 days + 5 epagomenal days (abandoned after Napoleon)
- International Fixed Calendar (proposed 1930s): 13 months × 28 days + 1 extra day (never adopted, opposed by religious groups)
7. What is a leap year and how does it affect months?
Leap year: Year with 366 days (not 365), adding 1 extra day to February (29 days instead of 28).
Leap year rule (Gregorian calendar):
- Year divisible by 4 = leap year (e.g., 2024)
- EXCEPT century years (1700, 1800, 1900) = NOT leap year
- EXCEPT century years divisible by 400 (1600, 2000, 2400) = leap year
Why leap years? Solar year = 365.2422 days (not exactly 365), so calendar gains ~0.2422 days per year = ~1 day every 4 years. Adding leap day keeps calendar aligned with seasons.
Impact on months:
- Only February affected (28 → 29 days)
- Leap year: 366 days = 52 weeks + 2 days (52.29 weeks)
- Non-leap year: 365 days = 52 weeks + 1 day (52.14 weeks)
Next leap years: 2024, 2028, 2032, 2036, 2040
8. What is the origin of month names?
Month names (Gregorian calendar, from Latin):
| Month | Origin | Meaning | |-----------|-----------|-------------| | January | Janus (Roman god) | God of beginnings, doorways (two faces looking forward/backward) | | February | Februa (Roman purification festival) | Purification ritual held mid-February | | March | Mars (Roman god) | God of war (originally first month of Roman year) | | April | Aprilis (Latin) | "To open" (buds opening in spring) or Aphrodite (Greek goddess) | | May | Maia (Roman goddess) | Goddess of growth, spring | | June | Juno (Roman goddess) | Goddess of marriage, queen of gods | | July | Julius Caesar | Roman dictator (month of his birth), originally Quintilis ("fifth") | | August | Augustus Caesar | First Roman emperor, originally Sextilis ("sixth") | | September | Septem (Latin) | "Seven" (originally 7th month before January/February added) | | October | Octo (Latin) | "Eight" (originally 8th month) | | November | Novem (Latin) | "Nine" (originally 9th month) | | December | Decem (Latin) | "Ten" (originally 10th month) |
Historical shift: September-December originally matched their numeric names (7th-10th months) when Roman year started in March. Adding January/February shifted them to 9th-12th positions.
9. Why is February the shortest month?
Roman superstition and politics:
- Roman numerology: Romans considered even numbers unlucky, so most months had 29 or 31 days (odd numbers)
- February = unlucky month: Month of purification rituals (Februa), associated with death/underworld, so Romans kept it short
- Julius Caesar's reform (46 BCE): Distributed days to create 365.25-day year, February remained shortest at 28 days
- Augustus's adjustment (8 BCE): Legend says Augustus took 1 day from February (29 → 28) to make August 31 days (matching July), but historians dispute this—likely just continued existing pattern
Result: February = 28 days (29 in leap years), shortest month by 1-3 days.
10. What are the financial quarters?
Financial quarters (Q1, Q2, Q3, Q4): 3-month periods dividing the fiscal year for business reporting.
Calendar year quarters:
- Q1 = January, February, March (90/91 days)
- Q2 = April, May, June (91 days)
- Q3 = July, August, September (92 days)
- Q4 = October, November, December (92 days)
Fiscal year variations: Many companies/governments use different fiscal years:
- US federal government: Oct 1 - Sep 30 (Q1 = Oct-Dec)
- UK government: Apr 1 - Mar 31 (Q1 = Apr-Jun)
- Japan/India: Apr 1 - Mar 31
- Australia: Jul 1 - Jun 30
Why quarters? Balance between frequent reporting (not too infrequent like annual) and manageable workload (not too frequent like monthly for major reporting).
11. How do I calculate age in months?
Formula: (Current year - Birth year) × 12 + (Current month - Birth month)
Example 1: Born March 15, 2020, today is June 15, 2024
- (2024 - 2020) × 12 + (6 - 3) = 4 × 12 + 3 = 51 months old
Example 2: Born November 20, 2022, today is January 10, 2024
- (2024 - 2022) × 12 + (1 - 11) = 2 × 12 - 10 = 14 months old
Precision note: Calculation above assumes same day of month. For exact age:
- If current day ≥ birth day: Use formula above
- If current day < birth day: Subtract 1 month (haven't reached full month yet)
When to use months for age:
- 0-23 months: Infant/toddler development changes rapidly monthly
- 24+ months: Typically switch to years ("2 years old" not "24 months old")
12. What's the difference between bi-monthly and semi-monthly?
Confusing terminology:
Bi-monthly = Ambiguous (avoid using)
- Meaning 1: Every 2 months (6 times per year)
- Meaning 2: Twice per month (24 times per year)
Semi-monthly = Twice per month (24 times per year)
- Example: Paycheck on 1st and 15th of each month
- 12 months × 2 = 24 pay periods per year
Bi-weekly = Every 2 weeks (26 times per year, not 24)
- Example: Paycheck every other Friday
- 52 weeks ÷ 2 = 26 pay periods per year
Recommendation: Avoid "bi-monthly" (ambiguous). Use "every 2 months" (6×/year) or "twice per month"/"semi-monthly" (24×/year).
About Century (c)
1. How many years are in a century?
Exactly 100 years. The word "century" comes from Latin "centum" (one hundred).
Other units:
- 1 century = 100 years = 10 decades = 1,200 months = ~36,525 days
2. When did the 21st century begin?
Formal answer: January 1, 2001 (because there was no year 0, the 1st century was years 1-100, so the 21st century is 2001-2100).
Popular answer: January 1, 2000 (most people celebrated the new millennium in 2000, and colloquially refer to "the 2000s" as the start of the 21st century).
Reality: Both are used; formal definition is technically correct, but popular usage dominates in practice.
3. Why is the 1800s called the 19th century?
Because of how centuries are numbered:
- 1st century = years 1-100
- 2nd century = years 101-200
- 18th century = years 1701-1800
- 19th century = years 1801-1900 (the "1800s")
- 20th century = years 1901-2000 (the "1900s")
Rule: Century number = (hundreds digit + 1). So 1800s → century 18+1 = 19th century.
4. How many generations are in a century?
Approximately 4-5 generations, assuming ~20-25 years per generation.
Calculation:
- If generation = 25 years → 100 ÷ 25 = 4 generations per century
- If generation = 20 years → 100 ÷ 20 = 5 generations per century
Example: Great-great-grandparents often lived in a different century than you.
5. Is a century a standard unit in science?
No. The century is not part of the International System of Units (SI). The SI base unit for time is the second.
Scientific time units:
- Years (Julian year = 365.25 days exactly)
- Kiloyears (kyr): 1,000 years
- Megayears (Myr): 1,000,000 years
- Gigayears (Gyr): 1,000,000,000 years
Century usage: Common in history, demography, climate science, but not formal SI unit.
6. How many days are in a century?
Approximately 36,525 days (accounting for leap years).
Calculation:
- 100 years × 365 days = 36,500 days
- Plus ~25 leap days per century = 36,525 days total
Exact number varies: Depends on leap year distribution (Gregorian calendar: 97 leap years per 400 years).
7. What is the difference between centennial and bicentennial?
Centennial: 100th anniversary (1 century)
Bicentennial: 200th anniversary (2 centuries)
Other -ennial terms:
- Sesquicentennial: 150th anniversary (1.5 centuries)
- Tercentennial/Tricentennial: 300th anniversary (3 centuries)
- Quadricentennial: 400th anniversary (4 centuries)
- Quincentennial: 500th anniversary (5 centuries)
8. Can a person live in three different centuries?
Yes, but extremely rare.
Requirements:
- Born in one century (e.g., 1898, 19th century)
- Live through next century (1900s, 20th century)
- Live into third century (2000s, 21st century)
- Requires living 102+ years if born in last years of century
Example: Born December 1898 (19th century) → lived through 20th century (1901-2000) → died January 2001 (21st century) = lived in 3 centuries despite being only 102 years old.
9. What is a "long century" in history?
Historical concept: Period longer than 100 years but representing a coherent historical era.
Famous examples:
- "Long 19th century" (1789-1914): French Revolution to WWI start
- "Long 18th century" (1688-1815): Glorious Revolution to Waterloo
- "Short 20th century" (1914-1991): Conversely, WWI to USSR collapse = only 77 years but captures coherent era
Why useful: Historical eras don't align neatly with formal century boundaries; "long/short century" captures thematic unity.
10. How do I calculate how many centuries between two years?
Formula: centuries = (ending year - starting year) ÷ 100
Examples:
- 1500 to 2000: (2000 - 1500) ÷ 100 = 5 centuries (500 years)
- 1776 to 2024: (2024 - 1776) ÷ 100 = 2.48 centuries (~248 years)
- 1900 to 2100: (2100 - 1900) ÷ 100 = 2 centuries (200 years)
11. What is "fin de siècle"?
French phrase: "End of the century" (literally "end of era")
Historical meaning: Cultural period at end of 19th century (1890s-1900s) characterized by:
- Cultural pessimism mixed with optimism
- Decadence, Art Nouveau
- Anxiety about modernity
- Transition into new century
Modern usage: Any "end of century" cultural moment (Y2K was modern "fin de siècle").
12. How many centuries in a millennium?
10 centuries = 1 millennium
Conversions:
- 1 century = 0.1 millennia (100 years)
- 5 centuries = 0.5 millennia (500 years)
- 10 centuries = 1 millennium (1,000 years)
- 20 centuries = 2 millennia (2,000 years)
Conversion Table: Month to Century
| Month (mo) | Century (c) |
|---|---|
| 0.5 | 0 |
| 1 | 0.001 |
| 1.5 | 0.001 |
| 2 | 0.002 |
| 5 | 0.004 |
| 10 | 0.008 |
| 25 | 0.021 |
| 50 | 0.042 |
| 100 | 0.083 |
| 250 | 0.208 |
| 500 | 0.417 |
| 1,000 | 0.833 |
People Also Ask
How do I convert Month to Century?
To convert Month to Century, enter the value in Month in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our time converter page to convert between other units in this category.
Learn more →What is the conversion factor from Month to Century?
The conversion factor depends on the specific relationship between Month and Century. You can find the exact conversion formula and factor on this page. Our calculator handles all calculations automatically. See the conversion table above for common values.
Can I convert Century back to Month?
Yes! You can easily convert Century back to Month by using the swap button (⇌) in the calculator above, or by visiting our Century to Month converter page. You can also explore other time conversions on our category page.
Learn more →What are common uses for Month and Century?
Month and Century are both standard units used in time measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our time converter for more conversion options.
For more time conversion questions, visit our FAQ page or explore our conversion guides.
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Verified Against Authority Standards
All conversion formulas have been verified against international standards and authoritative sources to ensure maximum accuracy and reliability.
National Institute of Standards and Technology — Official time standards and definitions
Bureau International des Poids et Mesures — Definition of the SI base unit for time
Last verified: December 3, 2025