Add Subtract Time Calculator.
Use this Add/Subtract Time calculator to quickly work out what the date and time will be after adding (or subtracting) a duration. It’s ideal for planning shifts, estimating deadlines, calculating arrival times, or working backwards from a target time.
Enter a start date and time, choose whether to add or subtract, and then enter the number of days, hours, and minutes. The result updates instantly.
Add/Subtract Time Calculator
Add or subtract days, hours and minutes from a chosen date and time. Results update instantly as you type.
How to use the calculator
- Select a Start date (optional).
- Enter a Start time (required).
- Choose Add or Subtract.
- Enter the days, hours, and minutes you want to apply.
- View the resulting date and time immediately. Use Reset to start over.
If you leave the start date blank, the calculator uses today’s date.
What this calculator is useful for
- Working out the finish time of a shift or a meeting
- Estimating delivery windows or travel times
- Adding time to a timestamp for project deadlines
- Subtracting time to find when you need to start to hit a target time
Examples
Example 1: Add time to a date and time
Start: 5 January 2026, 09:15
Add: 0 days, 2 hours, 45 minutes
Result: 5 January 2026, 12:00
Example 2: Subtract time to work backwards
Start: 5 January 2026, 18:30
Subtract: 0 days, 1 hour, 20 minutes
Result: 5 January 2026, 17:10
Example 3: Crossing midnight
Start: 5 January 2026, 23:30
Add: 0 days, 2 hours, 0 minutes
Result: 6 January 2026, 01:30
FAQs About Add/Subtract Time Calculator
How do I add time to a date and time?
Enter the start date/time, choose Add, and enter your days/hours/minutes. The result updates instantly.
How do I subtract time from a time?
Enter the start time (and date if needed), choose Subtract, then enter the duration to subtract. The calculator will show the new date/time.
What happens if the result crosses midnight?
The calculator automatically rolls into the next or previous day and updates the date accordingly.
Why can results vary around Daylight Saving Time?
When the clocks change, a day can be 23 or 25 hours in local time. The calculator uses your device’s local time zone, so results across that boundary can reflect this.
Can I leave the start date blank?
Yes. If you leave it blank, the calculator uses today’s date and applies your chosen start time.