For 1 hour 23 minutes, type "1", "2", "3". BIG KEYS, EASY TO TOUCH The number of keys is minimized, and the size of key is optimized. "60 MINUTES WARNING" Automatically stops calculation for a time input with 60 minutes or more. FEATURES: - Addition of time - Subtraction of time - History of entries - Revision of entries - Re-calculation of entries LIMITATIONS: Maximum time entry 999999999 hours 59 minutes Minimum time entry -99999999 hours 59 minutes