Everyday tools · runs locally
Work out dates and gaps
Days between two dates, a date plus 90 days, or an exact age — without counting on your fingers.
- 1Pick a mode
Difference, add/subtract, or age. Each mode has its own two or three fields.
- 2Enter the dates
Use the date pickers. Calendar dates are compared directly, without time-zone shifts.
- 3Read or copy the result
The answer includes the long form, total days, and the extra numbers that usually matter.
What this tool does
The calculator works with calendar dates rather than timestamps. Mixing local time and UTC is a classic source of off-by-one errors, especially around daylight-saving changes, so the inputs are parsed as UTC midnight and compared there.
Age mode also reports the weekday you were born on and the number of days until the next birthday. Add/subtract mode clamps month ends instead of overflowing into the next month.
Questions people actually ask
How is the difference counted?
As calendar dates in UTC. The result shows an exact years/months/days breakdown plus the total number of days, weeks and weekdays.
Why does 31 January plus one month land in February?
Months are clamped to the last valid day. 31 January + 1 month becomes 28 or 29 February rather than spilling into March.
Does it include the end date?
The day difference counts the gap between the dates, so 1 January to 2 January is 1 day. That is the usual convention for deadlines and ages.
Are leap years handled?
Yes. The date arithmetic uses the real calendar, including 29 February.