Year (yr) - Unit Information & Conversion
What is a Year?
Definition
A year is a unit of time based on the orbital period of the Earth around the Sun. A standard calendar year has 365 days, while a leap year has 366 days. For scientific and conversion purposes, the Julian year is often used, defined as exactly 365.25 days (or 31,557,600 seconds).
History
Calendars have been developed since antiquity to track the seasons, crucial for agriculture. Early calendars (e.g., Egyptian) approximated the solar year. The Julian calendar introduced the leap year concept (every 4 years) to better align with the ~365.25 day solar year. The Gregorian calendar refined this further by adjusting the leap year rule (skipping leap years in century years not divisible by 400) for even greater accuracy relative to the tropical year (time between vernal equinoxes).
Common Uses
- Calendars & Dating: The fundamental unit for long-term dating and tracking historical events.
- Age: Standard unit for measuring the age of people, animals, objects, and historical periods.
- Cycles: Measuring long durations such as astronomical cycles, geological periods, project timelines, fiscal periods (fiscal year), academic periods (academic year).
- Anniversaries & Celebrations: Marking annual events like birthdays, holidays, and anniversaries.
- Interest Rates & Finance: Often used as the basis for calculating annual interest rates (APR) and financial reporting.
Unit FAQs
How many days are in a year?
A common year has 365 days. A leap year has 366 days.
What is a leap year?
A leap year occurs generally every 4 years and includes an extra day (February 29th) to keep the calendar year synchronized with the astronomical or seasonal year.
Why is 365.25 days often used for a year in calculations?
This represents the average length of a year in the Julian calendar system, accounting for the leap day every four years. It provides a consistent value for conversions and scientific contexts.
How many seconds are in a Julian year?
There are 31,557,600 seconds in a Julian year (365.25 days * 86,400 seconds/day).
Year Conversion Formulas
To Second:
To Minute:
To Hour:
To Day:
To Week:
To Month:
To Millisecond:
To Microsecond:
To Nanosecond:
To Decade:
To Century:
To Millennium:
To Fortnight:
To Planck Time:
To Shake:
To Sidereal Day:
To Sidereal Year:
Convert Year
Need to convert Year to other time units? Use our conversion tool.