Date calculator & D-day
Compare two dates, count down to an event, or add days, weeks, months and years in one date calculator. Files and entered content are not sent to or stored on a server.
How to use
Compare two dates, count down to an event, or add days, weeks, months and years in one date calculator.
Please note
Date differences ignore daylight saving and time of day. Inclusive counts include both endpoints; same-day dates count as 1 day.
Date calculator & D-day User guide
Instructions
- Choose Date difference / D-day or Add / subtract dates.
- Choose the dates, or use today. For addition, enter an integer and a unit; negative amounts subtract.
- Read and copy the live result. Enable inclusive day counting to treat the start date as day 1.
Example
Input / settings
2026-01-31 + 1 month
Result / checks
2026-02-28
Please note
- Date differences ignore daylight saving and time of day. Inclusive counts include both endpoints; same-day dates count as 1 day.
- Use calendar dates in years 0001–9999. Inputs are saved only in this browser; the today option follows this device's date.