About the date calculator
The date calculator works two ways: it counts the time between two dates, or it adds or subtracts years, months, weeks and days from a starting date to find a new date. It can count calendar days or business days (Monday to Friday), skipping any holidays you list.
It is handy for contract deadlines, project schedules, notice periods, delivery estimates and any question that starts with “how many days until…” or “what date is… from now”.
Who should use the date calculator
- Project managers and freelancers setting deadlines.
- Anyone calculating a notice period, warranty end or trial length.
- People planning travel, pregnancy-related dates, events or countdowns.
How to use the date calculator: what each input means
- Mode
- Days between two dates, or add/subtract time from a date.
- Start and end dates
- In between mode both are used. The end date can optionally be included in the count.
- Years, months, weeks, days
- The amount to add or subtract.
- Count days as
- Calendar days, or business days that skip weekends and your list of holidays.
- Holidays
- Optional list of dates in YYYY-MM-DD format that should not count as business days.
How the date calculator works: method and formula
Calendar-day differences are exact counts of midnight-to-midnight days, so daylight-saving changes do not affect them. The elapsed time is also broken into years, months and days using the same rule as the age calculator.
When adding months, if the target month is shorter than the starting day (for example 31 January plus one month), the result is the last day of that month. Business-day counting skips Saturdays, Sundays and any listed holiday.
- Days between
- days = end date − start date (+1 if the end date is included)
How to read your date calculator result
The headline gives the main answer; the extra lines show the same period in weeks, months and business days. When you add business days, the result date skips non-working days, so it may be more than a week away for five business days.
Public holidays differ by country and region, so the calculator does not guess them. Add the ones that apply to you.
Date Calculator worked example
From 15 January 2025 to 1 March 2025.
- Calendar days between the dates: 45.
- That is 1 month and 14 days, or 6 weeks and 3 days.
- Weekdays (Monday to Friday) in that period, not counting the end date: 33.
- Going forward instead: 15 January 2025 plus 45 days is Saturday, 1 March 2025.
45 days between the two dates; adding 45 days to 15 January 2025 gives Saturday, 1 March 2025.
Practical uses of the date calculator
- Calculating when a 30-day trial or a 14-day cooling-off period ends.
- Counting working days until a delivery or deadline.
- Finding a date a set number of weeks ahead.
Assumptions and limitations of this calculator
- Holidays are not built in because they vary by country and year; list the dates you want to skip.
- Calendar dates only, with no time-of-day or time-zone handling.
- Legal deadlines can have specific counting rules (for example whether the first day counts). Check the rule that applies to you.
Notes for different countries and units
- Business days are counted as Monday to Friday, skipping Saturdays, Sundays and any holiday dates you list in YYYY-MM-DD format. If your country has a different working week or its own public holidays, list the extra dates yourself.
- Date pickers show dates in the format your browser or device uses, usually DD/MM/YYYY in the UK, Europe, India and Pakistan and MM/DD/YYYY in the US. The calculation does not depend on the display format.