About this tool

This calculator adds or subtracts a span of hours, minutes, and seconds from a clock time, automatically wrapping around midnight when needed. It flags whenever the result rolls over to the next day or back to the previous one, so you always know if a shift or schedule change crosses a day boundary.

Common uses

• Working out what time a shift ends after a set number of hours
• Scheduling a follow-up call a fixed number of minutes later
• Reverse-calculating a start time from a known end time