Days to Seconds (days to s)

How to convert days to seconds

Multiply the days by 86,400:

s = days × 86,400

7 days × 86,400 = 604,800 s. The factor is exact: a day is 24 hours, an hour 60 minutes and a minute 60 seconds, so 24 × 60 × 60 = 86,400. The result also shows hours and minutes. To go the other way, divide seconds by 86,400.

Days to seconds chart

Seconds in software and science

Computers store time as seconds or milliseconds since January 1, 1970, so settings written in seconds are common: a cache that expires after 86,400 seconds lasts one day, and a token valid for 604,800 seconds lasts a week. Converting a timeout or an interval from days to seconds avoids an off-by-a-thousand mistake when the setting is in milliseconds: one day is 86,400,000 ms. For milliseconds, see milliseconds to seconds.

Leap seconds and clock changes

A few days have not been exactly 86,400 seconds long. Between 1972 and 2016, 27 leap seconds were added to keep clocks in step with Earth’s rotation, giving those days 86,401 seconds; international timekeepers have agreed to stop adding them by 2035. Separately, the days when daylight saving time starts and ends have 23 and 25 hours on local clocks — 82,800 and 90,000 seconds — though the physical day is the same length. For counting the hours between two clock times across such a change, use the time duration calculator.

Big numbers made smaller

Large counts of seconds are easier to read in days. A million seconds is 11.6 days, and a billion seconds is about 31.7 years, which is why “a billion seconds old” falls in a person’s early thirties. Unix time, the seconds counted since January 1, 1970, passed 1.7 billion in November 2023; dividing by 86,400 gives the number of days since 1970. The 32-bit version of that counter overflows at 2,147,483,647 seconds, on January 19, 2038, and systems still using it must be updated before then.

Days, hours and minutes

The same factors give the smaller units: a day is 24 hours, 1,440 minutes or 86,400 seconds. For a list of durations from a log or a config file, open Convert a list of values and paste the days one per line. For hours, see hours to days; for minutes, how many minutes are in a day.