Date Calculator
Count the days between two dates, add or subtract time from a date, or measure hours between two times.
Results are provided as is, for general information. Check anything important before relying on it. See the Terms of Use.
About this tool
Three modes in one calculator: days between two dates, add or subtract a span from a date, and the elapsed time between two moments. Days between dates counts the span and expresses it five ways at once: total days, weeks plus days, calendar months plus days, years plus months plus days, and business days (Monday to Friday, no holidays). Results are signed — a to-date before the from-date yields negatives — so the tool never guesses which direction you meant. Month arithmetic clamps end-of-month dates the intuitive way (Jan 31 plus one month reaches Feb 28), and all math runs in UTC, so daylight-saving transitions cannot make a day count off by one. Add or subtract moves a start date by years, months, weeks and days and names the weekday of the result. Date and time gives the elapsed days, hours, minutes and seconds between two clock readings.
How it works
Days = later date − earlier date (calendar days) Weeks = Days ÷ 7 (whole weeks + remainder days) Business days = Monday–Friday dates after the start date, up to and including the end date Add or subtract: move years and months first (day clamped to the month end), then add weeks × 7 + days Elapsed time = end − start in seconds, split into days, hours, minutes and seconds
The gap is counted in calendar days, so daylight-saving changes never add or remove a day. Business days skip Saturdays and Sundays but not public holidays, and the start date itself is not counted. Adding or subtracting moves months in one step from the start date; times are compared as one clock with no time zone.
| Question | Working | Answer |
|---|---|---|
| How many days from 1 January to 1 March 2025? | 31 + 28 | 59 days (2 months, 8 weeks 3 days) |
| How many business days from Monday 3 March to Friday 14 March 2025? | 11 calendar days minus 1 weekend of 2 days | 9 business days |
| What date is 3 months and 10 days after 17 October 2026? | 17 October + 3 months = 17 January 2027, then + 10 days | Wednesday, 27 January 2027 |
| How many hours from 08:00 to 17:30 on the same day? | 17:30 − 08:00 = 9 h 30 min = 570 min | 9.5 hours (570 minutes) |
When to use it
Questions
How many days are there between two dates?
Subtract the earlier date from the later one in calendar days. 1 January to 1 March 2025 is 31 + 28 = 59 days. The start date is not counted and the end date is, so the same date twice is 0 days. Enter both dates and the result also shows weeks, months, years and business days.
Why does the month count not always match days ÷ 30?
Months have different lengths, so the tool counts real month-boundary crossings and then the leftover days — 2026-01-01 to 2026-03-01 is 2 months and 0 days (59 days total), not 1 month and 29 days. Advancing past a short month clamps the day: Jan 31 plus one month lands on Feb 28.
What counts as a business day?
Any Monday-to-Friday date in the range — public holidays are not excluded because they differ by country and year. The count is signed with the range, and both endpoints follow the same rule: the day after the earlier date through the later date.
Why did I get a negative number?
You put the later date in the From field. Output is deliberately signed rather than silently swapped, so "minus 59 days" tells you the direction instead of hiding the mistake.
How are business days counted?
Monday-to-Friday dates strictly after the earlier date, through the later date inclusive — so a weekend-only span counts zero. Public holidays are not subtracted: they differ by country and year, and a static list would silently miscalculate for everyone outside it. Subtract your own region's holidays from the figure; the tool is the base count, not the final word.
Why does Jan 31 plus one month land on Feb 28?
The month arithmetic clamps to the target month's length, because February has no 31st: Jan 31 + 1 month is Feb 28 (Feb 29 in a leap year). In Days between dates mode the months are counted one step at a time and clamped at every step, so Jan 31 to Mar 31 reads as 2 months and 3 days. Add or subtract mode makes one jump from the start date, so Jan 31 + 2 months is Mar 31. Both are accepted conventions; the one-jump rule is what spreadsheets use for adding months.
Which unit should I read — days, weeks, months or years?
Whichever the obligation you are measuring speaks: leases and contracts in calendar months (with clamping as above), interest and payroll in days, project planning in weeks plus days, ages and warranties in years. All five readings derive from the same two dates, so they agree with each other — but they are different statements, not roundings of one number: 59 days and '2 months' describe the same span in different unit systems.
Does time of day or time zone matter?
Not in Days between dates or Add or subtract: those use plain calendar dates in UTC, so a day is a day whether a daylight-saving change falls inside the range or not. Date and time mode compares two clock readings as if they were on the same clock, with no time zone, so a span that crosses a daylight-saving change is counted as the clock shows it, without adding or removing the hour. Use the time zone converter first if the two readings are in different zones.
How do I add days, weeks or months to a date?
Choose Add or subtract, pick the start date and enter the years, months, weeks and days to add; leave a box empty for zero. Years and months move first, then weeks and days are counted as calendar days. 17 October 2026 plus 3 months and 10 days is 27 January 2027, a Wednesday. Switch to Subtract to go backwards, for example to find the date 90 days before a deadline.
How do I find the hours between two times?
Choose Date and time, then enter a start and an end date and time. The result shows the elapsed days, hours, minutes and seconds, plus the totals in hours, minutes, seconds and days. 8:00 to 17:30 on the same day is 9 hours 30 minutes, or 9.5 hours. For a shift that runs past midnight, set the end date to the next day. This is elapsed time, so it does not subtract breaks.
Why is my result negative?
The later date sits in the From field. Output is signed rather than silently swapped, so '−16 days' tells you the direction, which an unsigned 16 would hide — useful when the from/to fields arrive from a template or a script and the order is easy to get backwards. Swap the dates for the positive span.
Can the day count and the month count seem to disagree?
They measure different segmentations, so yes — 2026-01-01 to 2026-03-01 is simultaneously 59 days, 8 weeks 3 days, and 2 months even, because the calendar months in between happen to sum to 59 days. End mid-month and remainders appear in the smaller units: the month count tallies real boundary crossings, the day count counts every day. Both are exact; neither is a rounding of the other.