Date Calculator
Calculate the number of days between two dates, or add and subtract days, weeks and months from a date. Business day mode included. Free.
On your device: nothing you enter here is uploaded.
Days between two dates
- Days
- 30
- Business days
- 20
- Weekend days
- 10
- Weeks
- 4.29
- Months
- 0
- Years
- 0.00
- Hours
- 720
Add or subtract from a date
What this tool is for
Two calculations that come up constantly: how long between these dates, and what date is N days from this one. Business day mode skips weekends, which is what deadlines, notice periods and delivery estimates are usually counted in.
What date is N days after a given date?
Pick the start date in the second panel, type the number of days and choose "add". The result is the calendar date that many days later, with the day of the week, so "90 days after March 3" or "45 days from today" is one step instead of counting squares on a calendar.
Day counts cross month and year boundaries correctly, including 29 February in leap years. Adding months is different from adding days: one month after 31 January is the last day of February, while 30 days after 31 January is 2 March in a common year.
Common periods in weeks and months
Notice periods, trial periods and payment terms are usually written in days, while people think in weeks and months. These are the usual equivalents. Months are approximate, because calendar months run from 28 to 31 days.
| Days | Weeks | Roughly |
|---|---|---|
| 7 | 1 week | one week |
| 14 | 2 weeks | half a month |
| 30 | 4 weeks 2 days | one month |
| 45 | 6 weeks 3 days | one and a half months |
| 60 | 8 weeks 4 days | two months |
| 90 | 12 weeks 6 days | three months, a quarter |
| 100 | 14 weeks 2 days | three and a third months |
| 120 | 17 weeks 1 day | four months |
| 180 | 25 weeks 5 days | six months |
| 365 | 52 weeks 1 day | one common year |
Should the start date be counted?
This is the most common source of off-by-one disagreements. By default the calculator counts the nights between two dates, so Monday to Tuesday is one day. Turn on "Count both endpoints" when the first and the last day both count, as in most contracts, leave requests and event durations. Hotel stays are the opposite case: three nights from Monday to Thursday.
Legal deadlines have their own rules that vary by country and court: some exclude the day of the triggering event, some move a deadline that falls on a weekend or public holiday to the next working day. The business day mode skips Saturdays and Sundays but does not know your local holidays, so check those by hand for anything with legal weight.
How to use it
- To measure a gap, set both dates and read the result in days, weeks, months and years.
- To shift a date, set the start and the amount to add or subtract.
- Turn on business days to skip Saturdays and Sundays.
Frequently asked questions
Is the end date included?
The difference is exclusive by default, so 1 March to 2 March is one day. There is a toggle to count both endpoints, which is how contract periods are usually expressed.
How are months counted?
By calendar, not by a fixed 30 days. Adding one month to 31 January gives 28 or 29 February, since there is no 31st.