Enter the two clock times
- Enter start and end times, including seconds if needed.
- Choose the same day, the next day, or enter how many days later it finishes.
- Calculate the duration and decimal totals, then copy or download the result.
Examples and formula
09:00 to 17:30 on the same day is 8 hours and 30 minutes: 8.5 total hours, 510 total minutes or 30,600 seconds. 23:45 to 00:15 with The next day selected is 30 minutes. Equal times on the same day give 0; equal times on the next day give 24 hours.
Total seconds = end day offset × 86,400 + end-clock seconds − start-clock seconds. Decimal hours = total seconds ÷ 3,600; decimal minutes = total seconds ÷ 60. The NIST guide’s time-unit table gives 60 seconds per minute, 3,600 per hour and 86,400 per day.
Assumptions, limits and privacy
This is a nominal clock-time interval with 24-hour days. It has no calendar dates or time zones and does not account for daylight-saving transitions, time-zone travel or leap seconds. To cross midnight, choose The next day or a later day. An earlier clock time does not automatically mean tomorrow. This does not determine payroll, paid breaks or billable time; no breaks are automatically deducted.
Clock times 00:00:00–23:59:59, whole seconds only; end day offset 0–36,500, whole days. An earlier end time on the same day is rejected. Enter midnight as 00:00:00 on the next day rather than 24:00. Browser time-picker presentation may use 12-hour or 24-hour notation.
Inputs stay in browser memory without uploads or saved time entries. CSV normalizes clock times to HH:mm:ss, exports exact integer seconds and six-decimal hour/minute totals. Display rounds decimal totals to six places. Reset restores examples and clears results. Undo action restores both times, the finish-day choice and the entered days-later value before Example, Swap or Reset. Editing starts a new state. Copy decimal hours copies only the number, rounded to six decimal places without thousands separators.
Is 8 hours 30 minutes equal to 8.30 hours?
No. 30 minutes is half an hour, so the decimal duration is 8.5 hours.
Will it adjust for daylight-saving time?
No. It uses clock times with a fixed 24-hour day model. Actual elapsed time across an offset change can differ.