Time Duration Calculator

Both date-times are read exactly as written and subtracted: end minus start in seconds. Every other figure is that number divided — 60 for minutes, 3,600 for hours, 86,400 for days, 604,800 for weeks — so a “day” here is always 24 hours. The breakdown splits the same seconds into whole days, hours, minutes and seconds. If the end is before the start the span is shown as a positive figure with a minus sign and a note, rather than being silently swapped.

Months are not a fixed length, so the calendar breakdown uses the rule people use for ages and anniversaries: step forward from the start one whole month at a time, keeping the start's day of the month, for as long as the result is not past the end; the remaining time is counted in days. When the start's day does not exist in a later month, the step lands on that month's last day (31 January + 1 month = 28 or 29 February), which is why 29 February 2024 → 28 February 2025 reads as exactly one year. The time of day takes part: 10 March 09:00 → 10 April 08:59 is 30 days, not a month. Other tools that count months from the end date, or that always treat a month as 30 days, can differ by a day.

No time zone is applied; the inputs are wall-clock readings. That is what a timesheet or a contract usually means, but across a daylight-saving change the real elapsed time is one hour more or less than the wall clock shows — a warning appears on any span of a day or more so you can allow for it. For durations between instants in different zones, convert both to UTC first (the Epoch Converter does that) and enter the UTC values.

Dates are entered as YYYY-MM-DD, with an optional 24-hour time HH:MM or HH:MM:SS (a space or a T between). Dates that do not exist, such as 31 February, are refused rather than rolled over. Add mode accepts days, hours and minutes, negative to subtract. The calendar is the proleptic Gregorian calendar used by every modern system. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.