Date Difference Calculator

Calculate the days, weeks, months and years between two dates – or add/subtract from a date.

Days Between Two Dates
About Date Calculations

This calculator uses PHP's DateTime class to compute exact differences using the proleptic Gregorian calendar. Leap years (29 February) are handled automatically.

Common uses
  • Counting down to a deadline, holiday or birthday
  • Working out contract or notice period end dates
  • Calculating age in days, weeks or working days
  • Project timeline planning (working days only)
  • Pregnancy due date or "weeks pregnant" calculations
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Frequently Asked Questions

Subtract the earlier date from the later date. This calculator does it for you and also shows the result in weeks, months and years. By default the start day is counted but the end day is not – tick "include end date" to count both.

Calendar days include every day of the week. Working days exclude Saturdays and Sundays (a 5-day work week). Tick the "exclude weekends" option to count only Monday–Friday between your two dates. UK bank holidays are not excluded automatically.

Switch to the "Add / Subtract" tab, pick your start date, choose how many days (or weeks, months, years) to add, and click calculate. The tool returns the resulting date and day of the week.

Months have 28–31 days, so 30 days only equals a month sometimes. If you need calendar-month accuracy (e.g. "3 months from today"), use the months unit instead of converting to days. Adding "1 month" to 31 January in PHP rolls forward to early March, which is normal.