How to use: Add or subtract time periods for scheduling, project planning, and time tracking. Choose operation (Add Time or Subtract Time). Enter two time periods using hours, minutes, and seconds fields. The calculator automatically handles overflow (e.g., 90 minutes converts to 1 hour 30 minutes). Perfect for calculating work hours, project duration, meeting schedules, travel time, cooking timers, and workout sessions. Example: Add 2 hours 45 minutes to 1 hour 30 minutes = 4 hours 15 minutes. Useful for payroll, time sheets, and event planning.