User manual
Time Calculator manual
Use exact duration arithmetic or shift a clock time by a duration without manually carrying minutes, seconds, or midnight rollover.
1. Choose a mode
Add / subtract durations combines signed duration rows. Clock time +/- duration moves one time of day forward or backward by an entered duration. Switching modes leaves each mode's values unchanged.
2. Enter duration components
Days, Hours, Minutes, and Seconds accept whole numbers from 0 through 999,999,999. Blank fields mean zero. Minutes and seconds may exceed 59 because the engine normalizes them after converting the row to integer seconds.
3. Add or subtract rows
The first duration row is the positive base. Later rows can be Add or Subtract. Add another time creates a new row up to the 20-row limit. Remove deletes an optional row and recalculates immediately.
4. Read a negative result
A negative total is valid. The app applies one minus sign to the complete normalized result, such as -1h 35m, rather than mixing negative values into individual components.
5. Shift a clock time
Enter a 24-hour clock time and a non-negative duration, then choose Add or Subtract. The result shows HH:MM:SS, a 12-hour equivalent, and whether the result is the same day, next day, previous day, or multiple days away.
6. Decimal and total views
Decimal hours divide the exact signed seconds by 3,600. Total minutes divide by 60. Both use deterministic fixed-point rounding to at most six decimal places; Total seconds remains the exact integer result.
7. Copy and reset
Copy result copies the result and representations, not a hidden history of your rows. Reset clears both modes after confirmation when meaningful values exist.
Limits
A day means exactly 24 hours. This app does not perform calendar date arithmetic, elapsed time between two separate timestamps, time-zone or DST conversion, payroll, weekly time-card logic, countdowns, or timers.