Are leap years handled?

Yes. Spans that cross 29 February are counted correctly. A leap year is any year divisible by four, except centuries not divisible by four hundred — 2000 was a leap year, 2100 will not be — and that is the rule used here.

Can I use dates in the past?

Yes. If the end date falls before the start date the two are swapped automatically and a note says so. In shift mode, choosing earlier moves backwards. The fields are the browser’s own date pickers, so any four-digit year works.

Can I use it to work out an age?

As an approximation, yes: put the birth date in the start field and today in the end field, and divide the month figure by twelve. Legal definitions of age differ by country, though, so do not use this figure where an official one is required.

Does it account for times or time zones?

No. It works with whole dates only, all handled as midnight UTC, so it cannot report a span in hours and minutes. The upside is that daylight-saving transitions never shift the count by a day.

Can it exclude public holidays?

No — weekends only. Holidays vary by country and move from year to year, and labelling a figure as business days without an accurate holiday table would be misleading. Subtract the holidays that fall inside the span from the figure shown.

What does the difference in days count?

It is the end date minus the start date, so 1 August to 2 August is one day. Counting both ends as whole days — the inclusive convention used by many contracts — gives two. When a rule says "within N days", check which convention it means, because the two differ by exactly one.

What does the business-day figure exclude?

Saturdays and Sundays only. Public holidays, company shutdowns and year-end closures are not accounted for. Business days are counted inclusively — Monday to Friday is five — while the difference in days is a subtraction, so the two figures use different conventions on purpose. ⚠️ Shift counts differently again: the starting date is not included, so five business days after a Friday is the following Friday (counting the start would land on the Thursday before).

What are the remainders in weeks and months?

Weeks are the day difference divided by seven, with the remainder shown beside it. Months are counted on the calendar first, and whatever is left over is expressed in days: 3 mo 5 d means the end date is five days after the start date advanced by three months. Because months differ in length, one month covers anything from 28 to 31 days.

How is the end of the month handled when shifting by months?

The result clamps to the last day of the target month, so 31 March plus one month is 30 April. That makes the operation non-reversible: going back a month from 30 April lands on 30 March, not 31. Use days as the unit when an exact count matters.

Back to all tools／ Calculators

Date calculator

Runs in your browserNothing is uploaded

Get the span between two dates in days, weeks, months and business days at once, or shift a date by days, weeks, months or business days. Dates you type never leave the browser.

Input

What to calculate

Start date

End date

Output

Enter a date and the figures appear.

The gap is given in four units at once. Business days exclude Saturdays and Sundays but not public holidays, which differ by country and move from year to year.

Or type what you want to work out

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Highlights

Business days alongside calendar days: Deadlines are usually counted in working days rather than calendar days. The span view shows business days next to days, weeks and months, and the shift view offers business days as a unit of its own.
Month arithmetic that lands on real dates: A month is not thirty days, so adding one to 31 January cannot land on 31 February. The target date clamps to the last day of the month instead: 28 February, or 29 in a leap year.
Immune to time zones and daylight saving: Every date is handled as midnight UTC, so a span that crosses a 23-hour or 25-hour day is still an exact number of days, and the same input gives the same answer wherever the page is opened.

How to use it

Choose what to calculate
Pick Span for the distance between two dates, or Shift a date to move a date forwards or backwards. Both date fields already contain today when the page opens.
Enter the dates
Span takes a start date and an end date; Shift takes a starting date plus how far to move, a unit (days, weeks, months or business days) and a direction. The Today button beside each field resets it to the current date.
Read the figures
The results update as you type. Span shows the difference in days, the span in weeks, the span in months and the number of business days; Shift shows the resulting date with its weekday and the gap in days. Copy the result writes the whole summary to the clipboard.

Reading the figures

What does the difference in days count?: It is the end date minus the start date, so 1 August to 2 August is one day. Counting both ends as whole days — the inclusive convention used by many contracts — gives two. When a rule says "within N days", check which convention it means, because the two differ by exactly one.
What does the business-day figure exclude?: Saturdays and Sundays only. Public holidays, company shutdowns and year-end closures are not accounted for. Business days are counted inclusively — Monday to Friday is five — while the difference in days is a subtraction, so the two figures use different conventions on purpose. ⚠️ Shift counts differently again: the starting date is not included, so five business days after a Friday is the following Friday (counting the start would land on the Thursday before).
What are the remainders in weeks and months?: Weeks are the day difference divided by seven, with the remainder shown beside it. Months are counted on the calendar first, and whatever is left over is expressed in days: 3 mo 5 d means the end date is five days after the start date advanced by three months. Because months differ in length, one month covers anything from 28 to 31 days.
How is the end of the month handled when shifting by months?: The result clamps to the last day of the target month, so 31 March plus one month is 30 April. That makes the operation non-reversible: going back a month from 30 April lands on 30 March, not 31. Use days as the unit when an exact count matters.

Questions

Are leap years handled?: Yes. Spans that cross 29 February are counted correctly. A leap year is any year divisible by four, except centuries not divisible by four hundred — 2000 was a leap year, 2100 will not be — and that is the rule used here.
Can I use dates in the past?: Yes. If the end date falls before the start date the two are swapped automatically and a note says so. In shift mode, choosing earlier moves backwards. The fields are the browser’s own date pickers, so any four-digit year works.
Can I use it to work out an age?: As an approximation, yes: put the birth date in the start field and today in the end field, and divide the month figure by twelve. Legal definitions of age differ by country, though, so do not use this figure where an official one is required.
Does it account for times or time zones?: No. It works with whole dates only, all handled as midnight UTC, so it cannot report a span in hours and minutes. The upside is that daylight-saving transitions never shift the count by a day.
Can it exclude public holidays?: No — weekends only. Holidays vary by country and move from year to year, and labelling a figure as business days without an accurate holiday table would be misleading. Subtract the holidays that fall inside the span from the figure shown.

Input

Output

Related tools

Highlights

How to use it

Choose what to calculate

Enter the dates

Read the figures

Reading the figures

Questions