Date Calculator
Calculate the number of days, weeks, months, or years between two dates. Add or subtract days from any date.
Days Between Dates
0
Weeks
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Months (approx)
โ
Years (approx)
โ
Working Days (approx)
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Result Date
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How to Use
Date Difference: Select a start and end date to see the exact number of days between them, along with weeks, months, years, and an estimate of working days.
Date Arithmetic: Pick a starting date, choose to add or subtract, enter an amount, and select the unit (days, weeks, months, or years) to find the resulting date.
Formula
Days = |Date2 โ Date1| / 86,400,000 ms Working days โ Total days ร (5/7) | Weeks = Days / 7 | Months โ Days / 30.44
Frequently Asked Questions
- Subtract the earlier date from the later date. Each day has exactly 86,400 seconds, so: days = (Date2 โ Date1) / 86,400,000 ms. This calculator handles month-length differences, leap years, and timezone edge cases automatically.
- A date difference is expressed in days, weeks, months, or years. Days are exact; months and years are approximations because not every month or year has the same length. This tool shows all four units so you can choose the most meaningful one for your context.
- Use the Date Arithmetic mode: pick a start date, choose Add, enter the number of days, and the result date appears instantly. Adding 30 days to January 15 gives February 14 (in a non-leap year), accounting for varying month lengths.
- Enter both dates in the Date Difference mode and the calculator shows the exact number of days. For example, from January 1 to December 31 of the same non-leap year is 364 days. Leap years add one extra day.
- Working days (business days) exclude weekends. A quick approximation is total days ร 5/7. For a precise count you need to subtract public holidays as well. This calculator uses the 5/7 approximation which is accurate to within ยฑ1 day for typical date ranges.
- Divide the total number of days by 7. This calculator shows both whole weeks and a remainder. For example, 30 days = 4 weeks and 2 days.
- Months are calculated by counting full calendar months between two dates. Because months have 28โ31 days, this figure is approximate. The formula used is: months = (years ร 12) + month difference + day fraction.
- An online date calculator can: find the number of days/weeks/months/years between dates, add or subtract days/weeks/months/years from a date, determine what day of the week a date falls on, and calculate deadlines or anniversaries. This tool covers the most common use cases.
- Elapsed time is the difference between a past date and today (or another reference date). Use the Date Difference mode, set the start date to the past event and end date to today, and read the result in whichever unit suits you.
- Use the Date Arithmetic mode: enter today as the start date, choose Add, and enter the number of days until your deadline. The calculator shows the exact calendar date of the deadline, accounting for month-end rollovers and leap years.