Divide by 86,400 — then split the remainder
One day is exactly 86,400 seconds (24 × 60 × 60). Dividing gives the day count as a decimal; the digits after the point are hours, minutes and seconds. To read it as d:h:m:s, take whole days first, then divide the leftover by 3,600 for hours, by 60 for minutes, and keep the final remainder as seconds.
Common second counts
| Seconds | Days (decimal) | d : h : m : s |
|---|---|---|
| 3,600 | 0.042 | 0 : 1 : 0 : 0 |
| 86,400 | 1.0 | 1 : 0 : 0 : 0 |
| 100,000 | 1.157 | 1 : 3 : 46 : 40 |
| 604,800 | 7.0 | 7 : 0 : 0 : 0 |
| 1,000,000 | 11.574 | 11 : 13 : 46 : 40 |
| 2,592,000 | 30.0 | 30 : 0 : 0 : 0 |
| 31,536,000 | 365.0 | 365 : 0 : 0 : 0 |
A Unix timestamp is just a second count from 1 January 1970; dividing it by 86,400 gives the number of days since that date.
The two mistakes people make
- A day is not 24,000 seconds. It is 86,400. The 24 is hours; each hour is 3,600 seconds, not 1,000.
- Round late, not early. A million seconds is 11.574 days, not 11 — that last fraction is over half a day of real time.
Common questions
How many seconds are in a day?
Exactly 86,400: 24 hours x 60 minutes x 60 seconds. Converters use this fixed figure and ignore leap seconds, which are added only occasionally and almost never matter for everyday math.
How many days is a million seconds?
A million seconds is about 11.6 days, or 11 days 13 hours 46 minutes 40 seconds exactly. A billion seconds, by contrast, is roughly 31.7 years.
How do I break a second count into days, hours, minutes and seconds?
Divide by 86,400 for whole days, take what is left and divide by 3,600 for hours, divide the remainder by 60 for minutes, and the final remainder is the seconds.
