Date difference calculator

How to use

The difference between two dates can be counted in days, weeks or months, and each answer serves a different purpose. Days are exact, weeks are days divided by seven and months are an average — calendars do not have equal months, so an exact month count would need a rule for each pair of dates.

• Count the days until a deadline, a trip or a contract term.
• Work out how long a project or a treatment lasted.
• Convert a period quoted in days into weeks or months.

1. Enter the first date.
2. Enter the second date — it can be before or after the first.
3. The result shows the difference in days, weeks and approximate months.

Formula

Days = |end − start| ÷ 86,400 s · Weeks = days ÷ 7 · Months ≈ days ÷ 30.436875

Example

From 1 March to 1 June there are 92 days, 13.14 weeks or about 3.02 months.

Limitations

• Both dates are read in UTC to avoid daylight-saving shifts of one hour that would flip a day count.
• Months are an average of the Gregorian year (30.436875 days); the exact month count depends on which months are involved.
• Business days are not counted here — weekends and holidays are included in the result.

Frequently asked questions