Date Calculator
Calculate the difference between two dates in days, weeks, months, and years — or add/subtract days to a date. Handles month and year boundaries correctly. 100% browser-based, no signup.
Date Difference
Get the precise number of days, weeks (with remainder), months, and years between two dates. Calendar-aware — borrows days from the preceding month, so Feb 28 → Mar 31 is exactly 1 month, 3 days.
Add / Subtract Days
Enter a start date and a positive or negative number of days to compute the resulting date. Works across month and year boundaries (e.g. Jan 28 + 5 days = Feb 2).
DST-Safe Math
Calculations use local noon and setDate arithmetic to avoid off-by-one errors around daylight-saving transitions. The result is always the calendar date you expect.
100% Private
All date math runs in your browser. No dates are uploaded to a server, no signup required, and there is no daily limit.
How is the date difference calculated?
Total days is the difference between the two dates in milliseconds divided by 86,400,000. The calendar breakdown (years, months, days) borrows days from the preceding month when the end day is earlier than the start day, so 1 month always means "same day next month".
How are weeks shown?
Weeks are total days ÷ 7 (rounded down). The remainder in days is also shown so you can see exactly "8 weeks and 3 days" instead of a fractional number.
What if the end date is before the start date?
The calculator still works — total days will be negative, and the calendar breakdown (years/months/days) is computed from the earlier date forward.
How does "add/subtract days" handle month boundaries?
It uses native JavaScript Date arithmetic: setDate(getDate() + n). The browser correctly rolls over to the next month or year. For example, January 28 + 5 days = February 2.
Are leap years handled?
Yes. JavaScript's native Date object understands leap years, so February 29 is valid in leap years and is handled correctly when subtracting days or computing differences.
Ready to use the Date Calculator?
Free, no signup, no watermark. 100% browser-based. Your data never leaves your device.
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