Guide
About Date Calculations
Counting days between dates
By default the result counts the days from the start date up to the end date, the way you would count nights in a hotel: Monday to Friday is 4 days. Turn on Include the end date to count both days, which is how you count days of an event or a vacation: Monday to Friday is 5 days.
The weekday count includes Monday to Friday only. Public holidays vary by country and region, so subtract any that apply to you.
Adding months
Months have different lengths, so "one month after January 31" has no exact answer. This calculator uses the common convention of moving to the last valid day of the target month: January 31 plus one month is February 28, or February 29 in a leap year. Years and months are added first, then weeks and days.
How ages are calculated
Age is counted in whole years, then whole months, then the remaining days since the last month boundary, the same way people state their age. People born on February 29 celebrate on February 28 in non-leap years here; some countries use March 1 for legal purposes.
Frequently asked questions
Does the calculator account for leap years?
Yes. All calculations use the real calendar, including February 29 in leap years (every 4 years, except century years not divisible by 400).
Are time zones or daylight saving involved?
No. The calculator works with whole calendar dates, so daylight saving changes cannot add or remove an hour from the result.
How many working days are in a year?
A year has 260 or 261 Monday-to-Friday days (262 in some leap years), before public holidays. Use the 'Days between' tab with January 1 and December 31 and include the end date to see the exact count.