Date / Time Calculator

Difference: enter two local dates and times. Results update immediately. They show elapsed time from From to To; swapping the dates reverses the sign. Days are exactly 24 hours and weeks are seven such days. Values are rounded to at most three decimal places.

Add / subtract: enter a start date and signed whole calendar days, hours and minutes. Calendar days are applied first using the local clock; hours and minutes then add elapsed time. In Europe/Berlin, 30 March 2024 at noon plus one calendar day is 31 March at noon (23 elapsed hours); plus 24 hours is 13:00. If the target clock time falls in a daylight-saving gap it moves forward by the gap; repeated times choose the earlier occurrence. A missing clock time entered directly is rejected.

The browser time zone is shown below the result. Inputs support positive Gregorian years within the browser Date range, at minute precision. This is not a holiday, business-day or recurring-event calculator. Reset restores the defaults in the active tab. Inputs and the selected tab survive navigation and reload.