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Day (d) - Unit Information & Conversion

Symbol:d
Plural:days
Category:Time

What is a Day?

Definition

A day is a unit of time typically defined as 24 hours, which is equivalent to 1,440 minutes or 86,400 seconds. It roughly corresponds to one full rotation of the Earth on its axis relative to the Sun (a solar day).

History

The concept of a day as a fundamental cycle of light and darkness is ancient. The division into 24 hours developed over time, notably influenced by the Egyptians. While the solar day (time between two successive solar noons) varies slightly throughout the year, the standard mean solar day of 86,400 SI seconds is used for civil timekeeping.

Common Uses

  • Civil Timekeeping: The primary unit for organizing daily life, calendars, schedules, and dates.
  • Astronomy: Used to measure rotational periods of planets and other celestial bodies (though the definition might differ, e.g., sidereal day).
  • Duration: Measuring the length of events, projects, trips, or lifespans that span multiple hours.
  • Biology: Studying circadian rhythms (biological processes that follow a roughly 24-hour cycle).
  • Work & Rest: Structuring periods of work, leisure, and sleep.

Unit FAQs

How many hours are in a day?

There are typically 24 hours in a standard civil day.

How many seconds are in a day?

There are 86,400 seconds in a standard 24-hour day (24 hours * 60 minutes/hour * 60 seconds/minute).

Is every day exactly 24 hours long?

The apparent solar day (time from one noon to the next) varies slightly due to the Earth's elliptical orbit and axial tilt. The mean solar day, used for clocks, averages this out to 24 hours. Leap seconds are occasionally added to keep clock time aligned with the Earth's rotation.

What's the difference between a solar day and a sidereal day?

A solar day is based on the Sun's position (approx. 24 hours). A sidereal day is based on the Earth's rotation relative to distant stars (approx. 23 hours, 56 minutes, 4 seconds).

Day Conversion Formulas

To Second:

1 d = 86400 s
Example: 5 days = 432000 seconds

To Minute:

1 d = 1440 min
Example: 5 days = 7200 minutes

To Hour:

1 d = 24 h
Example: 5 days = 120 hours

To Week:

1 d = 0.142857 wk
Example: 5 days = 0.714286 weeks

To Month:

1 d = 0.032855 mo
Example: 5 days = 0.164274 months

To Year:

1 d = 0.002738 yr
Example: 5 days = 0.01369 years

To Millisecond:

1 d = 86400000 ms
Example: 5 days = 432000000 milliseconds

To Microsecond:

1 d = 86400000000 μs
Example: 5 days = 432000000000 microseconds

To Nanosecond:

1 d = 86400000000000 ns
Example: 5 days = 432000000000000 nanoseconds

To Decade:

1 d = 0.000274 dec
Example: 5 days = 0.001369 decades

To Century:

1 d = 0.000027 c
Example: 5 days = 0.000137 centuries

To Millennium:

1 d = 0.000003 ka
Example: 5 days = 0.000014 millennia

To Fortnight:

1 d = 0.071429 fn
Example: 5 days = 0.357143 fortnights

To Planck Time:

1 d = 1.602671118530885e+48 tP
Example: 5 days = 8.013355592654425e+48 Planck times

To Shake:

1 d = 8640000000000 shake
Example: 5 days = 43200000000000 shakes

To Sidereal Day:

1 d = 1.002738 sidereal day
Example: 5 days = 5.01369 sidereal days

To Sidereal Year:

1 d = 0.002738 sidereal year
Example: 5 days = 0.013689 sidereal years

Convert Day

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Day Quick Info

d
Symbol:d
Category:Time
System:Various
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