Time Converter

Converting between seconds, minutes, hours, and days is straightforward until a unit stops being a fixed size. Seconds, minutes, and hours are constant. Days are constant for arithmetic but not on a calendar, because daylight saving makes two days a year 23 or 25 hours long in regions that observe it. Months are never constant, ranging from 28 to 31 days, and years alternate between 365 and 366. That is why converting 90 days to months gives you an approximation and converting 90 days to hours gives you an exact 2,160.

The practical rule: anything up to weeks converts exactly, anything involving months or years is an estimate unless you anchor it to real calendar dates.

Logs, video files, and APIs each report time differently, and the format tells you the unit. A duration written as 00:04:35 is hours:minutes:seconds, so 275 seconds. A media player showing 4:35 has dropped the leading hour field, still 275 seconds. A JSON field with 275000 is almost certainly milliseconds, the default for JavaScript and most web APIs. A value like 1735689600 with ten digits is a Unix timestamp in seconds, not a duration at all, and a thirteen-digit version of the same is milliseconds.

When a number seems wrong by a factor of 1,000, the unit is milliseconds. When it is wrong by 60 or 3,600, someone treated minutes as seconds or hours as minutes. Converting to a single base unit, usually seconds, before doing anything else removes most of these errors.

Freelance invoicing is the most common reason people convert time. Tracked work of 7,320 seconds is 2.03 hours, and most contracts round to the nearest quarter hour, so it bills as 2.0. Converting first and rounding second keeps the maths defensible if a client asks.

Video and audio work runs the other way: a 3 minute 42 second track is 222 seconds, which is what an editing timeline or an FFmpeg trim command expects. Deadlines convert differently again. A 72-hour SLA is three days only if the clock runs continuously; if it means three business days, the real elapsed time can be five calendar days across a weekend. Read which one the contract means before converting.