Features

• Three Calculation Modes — Add time, subtract time, or find the exact difference between two dates and times.
• Instant Results with Validation — Empty or negative inputs are flagged immediately, and the end date is validated to be after the start date.
• Smart Swap & Copy — One-click swap between Time 1 and Time 2 in add/subtract mode, plus one-click copy of the result to clipboard.
• Proper Result Labels Per Mode — Result card labels automatically switch between FIRST/SECOND/TOTAL (add/subtract) and START/END/DAYS (difference).
• 100% Private & Client-Side — All calculations happen locally in your browser; no data is uploaded or stored anywhere.