The day is a unit of time equal to 24 hours, or 86,400 seconds, representing one full rotation of the Earth on its axis.

What is a Day (Sidereal)?

The sidereal day is the time for Earth to rotate once relative to distant stars — approximately 23 hours, 56 minutes, and 4 seconds (86,164.0905 seconds).

Where is Day used in everyday life?

Calendar systems, hospital stays, travel itineraries, project deadlines, and food expiration dates.

What are common mistakes when converting Day?

Assuming all days are exactly 86,400 s — some days have leap seconds (86,401 s). Also, confusing calendar days with 24-hour periods.

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Day to Day (Sidereal)

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"1" Day

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Day (d)

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Picosecond(ps)Copy Answer
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Attosecond(as)Copy Answer
Nanosecond(ns)Copy Answer
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Millisecond(ms)Copy Answer
Second(s)Copy Answer
Minute(min)Copy Answer
Hour(h)Copy Answer
Week(wk)Copy Answer
Fortnight(fn)Copy Answer
Month (Average)(mo)Copy Answer
Month (Synodic)(mo (syn))Copy Answer
Year (365 days)(yr)Copy Answer
Year (Julian)(yr (Jul))Copy Answer
Year (Leap)(yr (Leap))Copy Answer
Year (Tropical)(yr (Trop))Copy Answer
Year (Sidereal)(yr (Sid))Copy Answer
Day (Sidereal)(d (Sid))Copy Answer
Hour (Sidereal)(h (Sid))Copy Answer
Minute (Sidereal)(min (Sid))Copy Answer
Second (Sidereal)(s (Sid))Copy Answer
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27 conversions shown

How to Convert Day to Day (Sidereal)

To convert days to hours: multiply by 24. To convert days to seconds: multiply by 86,400.

1 d = 24 h = 1,440 min = 86,400 s. A mean solar day is ~86,400.002 s due to Earth's slowing rotation.

For example, 1 Day (d) = 1.00273791 Day (Sidereal) (d (Sid)).

Day to Day (Sidereal) — Common Values

Quick reference conversion table showing common Day to Day (Sidereal) values for time measurement
Day (d)	Day (Sidereal) (d (Sid))
0.001	0.00100273791
0.01	0.0100273791
0.1	0.100273791
0.5	0.5013689549
1	1.00273791
2	2.005475819
5	5.013689549
10	10.0273791
15	15.04106865
25	25.06844774
50	50.13689549
75	75.20534323
100	100.273791
250	250.6844774
500	501.3689549
750	752.0534323
1000	1002.73791