Add / Subtract Time
Perform date arithmetic — add or subtract any duration from a date.
The Add or Subtract Time tool lets you apply duration offsets to any starting calendar date. Whether you need to determine a contract expiration date 90 days in the future, find when a 36-hour shipment will arrive, or calculate when a past event took place, this tool handles all calendar rollovers automatically.
How to Use the Add or Subtract Time
- Pick your starting date and time, or click "Current time" to begin from the present instant.
- Choose your desired mathematical operation: "Add (+)" or "Subtract (-)".
- Enter the duration values in days, hours, minutes, and seconds.
- Inspect the computed target date, time, and day of the week in the result box.
Key Features & Precision
Automatic Month & Year Rollover
Accurately navigates month-end boundaries (e.g. adding 15 days to February 20) including leap years.
Flexible Multi-Unit Inputs
Combine days, hours, minutes, and seconds in a single calculation (e.g. +14 days, 6 hours, 30 minutes).
Bidirectional Addition & Subtraction
Easily move forward into the future or backward into the past from any reference date.
Instant Formatted Results
Outputs human-friendly dates showing the full day of the week, calendar date, and exact clock time.
Common Use Cases
Legal & Warranty Deadlines
Calculate formal 30-day notice periods, warranty expirations, or trial periods.
Supply Chain & Shipping
Calculate estimated arrival dates by adding transit durations (e.g. 72 hours) to dispatch times.
Medical & Prescription Schedules
Determine follow-up appointment dates or course completion timelines after medical procedures.
Frequently Asked Questions
What happens when adding days rolls across February?
The calculation automatically detects leap years. Adding 10 days to February 25 in 2024 results in March 6 (leap year), whereas in 2025 it results in March 7.
Can I add only minutes or hours without changing the date?
Yes. You can leave the days field empty or at zero and add only hours and minutes to find target clock times.
Can I calculate backwards from a future deadline?
Yes. Select the future deadline as your starting date, choose "Subtract (-)", and input the prep duration to find when you must start.