⏱️ Runs while this tab is open. No install, no sign-up.
Enter a negative number to go backwards
How month-end is handled
31 January plus one month gives 28 February (29 in a leap year). Rather than rolling over into a date that does not exist, it clamps to the last day of that month.
What this tool does
- Add or subtract days, weeks, months, years
- Correct month-end handling (31 Jan + 1 month)
- Resulting weekday shown
- Quick 100-day and 1-year buttons
Other time tools
Timer and alarm sounds may not fire if the device goes to sleep.