Date difference calculator — days, weeks and months between two dates

How to use the date difference calculator

1. Choose a Start date.
2. Choose an End date. It starts as today, which makes “how long since” questions quick.
3. Tick Include the end date (count both days) if both days should count.
4. Read the Total days, then the breakdown: Years, months, days, Weeks, Total months, Weekdays (Mon–Fri) and Hours.
5. The From and To lines confirm the weekday of each date.

What it does and when to use it

Counting days on a calendar is slow and easy to get wrong, especially across months of different lengths and leap years. This tool gives the exact count instantly. Typical uses include the number of days until a trip or exam, how long ago an event happened, the length of a contract or notice period, days of a project, a baby’s age in days, or the number of weekdays in a school term.

For someone’s age from a birth date, the age calculator adds birthdays and the weekday of birth. To find the date a number of days from now, use add or subtract days, and for a live countdown, the countdown timer ticks down to the second.

How it works

Each date becomes a whole-number day count in the Gregorian calendar, worked out with integer formulas rather than the browser’s date object. The difference is then plain subtraction:

• Total days = later date − earlier date (+ 1 if the end date is included)
• Weeks = total days ÷ 7, shown as whole weeks plus days and as a decimal
• Years, months, days = the most whole calendar months that fit, then the days left over
• Weekdays = the days in the range that fall Monday to Friday
• Hours = total days × 24

Because no clock times are involved, time zones and daylight-saving changes cannot add or lose a day.

Worked examples

These are the calculator’s results.

A whole year, counted inclusively. 1 January to 31 December 2026 with the end date included: 365 days, exactly 1 year, 0 months, 0 days. Of these, 261 are weekdays, and the year has 8,760 hours.

Dates entered in reverse. Start 25 December 2024, end 29 February 2020. The calculator swaps them and reports 1,761 days, or 4 years, 9 months, 26 days, from Saturday 29 February 2020 to Wednesday 25 December 2024.

Today to Christmas. From Saturday 3 October 2026 to Friday 25 December 2026 is 83 days, which is 11 weeks and 6 days, or 2 months and 22 days, with 59 weekdays.

Limits and tips

• Holidays are not excluded from the weekday count.
• Times of day are ignored. For a difference in hours and minutes, compare the times separately.
• Historical dates before the Gregorian calendar was adopted in a country may not match records from that time.
• “Total months” counts only complete calendar months.