Plain DatesClear date calculations, with the rules shown.

Time arithmetic

Add or subtract hours and minutes

Start with a 24-hour time, enter a positive or negative duration, and see the resulting clock time with any day offset.

Calculate a clock time

How the duration is combined

Hours are converted to 60-minute units and added to the entered minutes. For example, −1 hour and 30 minutes combine to −30 minutes. Use matching signs if you intend both fields to move in the same direction.

Crossing midnight

23:30 plus 2 hours is 01:30 on the next day. The clock wraps to a 24-hour day while the separate day offset preserves the full result.

What this tool does not do

This is clock arithmetic without a date or time zone. It does not account for daylight-saving changes, time-zone offsets, work shifts, or elapsed time between timestamped events.

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