Days to Seconds Converter

Convert days to seconds — 86,400 by convention, though the Earth actually turns in 86,164 and is slowing down.

Conversion table

Days	In Seconds
0.5	43,200 s
1	86,400 s
1.5	129,600 s
2	172,800 s
2.5	216,000 s
3	259,200 s
4	345,600 s
5	432,000 s
6	518,400 s
7	604,800 s
8	691,200 s
9	777,600 s
10	864,000 s
12	1,036,800 s
15	1,296,000 s

📊 Seconds Worth Knowing

1 minute60 s
1 hour3,600 s
1 day86,400 s
1 week604,800 s
1 year (365 d)31,536,000 s
1 sidereal day86,164 s

When 86,400 Is Not the Whole Story

86,400 comes from 24 × 60 × 60. It is a convention of the clock, not a measurement of the Earth.
A sidereal day — one full rotation relative to the stars — is 86,164 seconds, about four minutes shorter than the solar day.
A day with a leap second is 86,401 seconds. There have been 27 of them since 1972, all added, never removed.
Unix timestamps pretend leap seconds do not exist: every Unix day is exactly 86,400. That is why timestamp maths and real elapsed time can disagree by 27 seconds.

Where 86,400 Comes From

The number is pure arithmetic on a convention: 24 hours × 60 minutes × 60 seconds. The 24 and the 60 are inherited, not derived — the Egyptians split day and night into twelve parts each, and the Babylonians counted in sixties. Neither choice has anything to do with the physics of the Earth. What did change is the second itself: since 1967 it has been defined as 9,192,631,770 oscillations of a caesium-133 atom, which means the second is now a property of an atom rather than a fraction of a day. A day is 86,400 of those seconds by agreement, and the Earth is asked to keep up.

The Earth Does Not Turn in 86,400 Seconds

It turns in 86,164.0905 seconds — the sidereal day, one full rotation measured against the fixed stars. The extra 236 seconds in a solar day exist because the Earth has also moved along its orbit, so it must turn a little further for the Sun to return to the same position in the sky. On top of that, tidal friction from the Moon is slowing the rotation by roughly 1.8 milliseconds per century, and the planet wobbles unpredictably as mass shifts in its core and oceans. The clock stays fixed at 86,400; reality drifts, and leap seconds are how the two are reconciled.

Leap Seconds and the 2035 Deadline

A leap second is an extra second inserted into UTC to keep clock time within 0.9 seconds of the Earth's actual rotation.
Twenty-seven have been added since 1972, always at the end of June or December. None has ever been removed.
A day containing one is 86,401 seconds long, and the clock reads 23:59:60 — a valid time that breaks a surprising amount of software.
In 2022 the General Conference on Weights and Measures voted to stop inserting leap seconds by 2035, letting UTC drift from solar time instead.
Google and Amazon avoid the problem with 'leap smear': they stretch the seconds either side so no clock ever shows 23:59:60.
The Earth has recently been spinning slightly faster, raising the odd prospect of a negative leap second — a day of 86,399 seconds that has never been tested.

Why Timestamp Maths Goes Wrong

Unix time counts seconds since 1 January 1970, but deliberately ignores leap seconds: every day is exactly 86,400.
That means the difference between two Unix timestamps is not the true elapsed time — it is short by however many leap seconds fell between them.
Dividing a timestamp difference by 86,400 gives you days, and that works precisely because Unix time is fictional in this one respect.
A 32-bit signed timestamp overflows on 19 January 2038, which is 2,147,483,647 seconds after the epoch.
Date arithmetic across a daylight-saving change also breaks: those days are 82,800 or 90,000 seconds, not 86,400.
For durations rather than dates, count seconds. For calendar dates, use a date library — the two problems are not the same problem.

Worked Examples

Common spans, converted

How many seconds in a day

24 hours × 60 minutes = 1,440 minutes
1,440 minutes × 60 seconds = 86,400 seconds
The Earth's actual rotation takes 86,164 s — 236 seconds less

1 day = 86,400 seconds by convention

A year, and why two answers exist

365 days × 86,400 = 31,536,000 seconds
A leap year: 366 × 86,400 = 31,622,400 seconds
Rule of thumb: π × 10⁷ seconds is within half a percent of a year

1 year ≈ 31.5 million seconds

Frequently Asked Questions

How many seconds are in a day?

86,400 seconds, from 24 × 60 × 60. That is a convention of the clock rather than a measurement: the Earth completes one rotation in 86,164 seconds, and the extra 236 seconds account for its movement along its orbit.

How many seconds are in a year?

31,536,000 for a 365-day year and 31,622,400 for a leap year. A useful approximation is π × 10⁷ seconds, which is accurate to within half a percent.

What is a leap second?

An extra second added to UTC to keep clock time within 0.9 seconds of the Earth's rotation. Twenty-seven have been added since 1972, and a day containing one lasts 86,401 seconds with a clock reading of 23:59:60.

Are leap seconds going away?

Yes. In 2022 the General Conference on Weights and Measures voted to stop inserting them by 2035. UTC will be allowed to drift from solar time instead, and some larger correction will be defined later.

Why does Unix time ignore leap seconds?

Because it was designed so that dividing by 86,400 always yields whole days. The trade-off is that the difference between two Unix timestamps is not the true elapsed time — it is short by the leap seconds that fell in between.

Is every day exactly 86,400 seconds?

No. Days with a leap second are 86,401. Days when daylight saving starts or ends are 82,800 or 90,000. Only the idealised clock day, and Unix time, are always exactly 86,400.