Date Calculator

The date calculator answers the two most common time questions: how many days are there between two dates, and what date falls a given number of days away. The difference is calculated in full years, months and days by the calendar, with a separate count of weekdays (Monday–Friday) and weekend days. The second mode adds or subtracts days from any date – handy for payment terms, vacations, warranties and deadlines.

How to use the calculator

“Difference between dates” mode: pick the first and the second date – the order does not matter. The calculator shows the full interval (years, months, days), the total number of days and weeks, and how many of them are weekdays and weekend days. “Date ± N days” mode: set the base date (today by default), the number of days and the direction – forward or back. The result comes with the day of the week, so you can see right away whether it is a working day.

How the difference between dates is calculated

The interval is computed by calendar rules: the earlier date is subtracted from the later one, and if there are not enough days they are borrowed from the previous month (which has 28–31 days); if there are not enough months, they are borrowed from the year. That is why from January 31 to February 28 there are exactly 28 days, not “one month minus three days”. The total days are simply the difference in days; weeks are the integer part of the division by seven. Weekdays are counted analytically, without iterating over days: full weeks contribute five working days each, and the remaining partial week is checked day by day.

Weekdays and holidays

The calculator treats Monday–Friday as weekdays and does not account for public holidays – their calendars differ from country to country and change every year. For an exact working-day count including holidays, subtract the holidays falling inside the interval from the number of weekdays manually.

Typical examples

How many days until New Year: pick today’s date and December 31 – you will see the exact number of days, weeks and weekdays. A “30 days from order” delivery term: in the “Date ± N days” mode enter the order date and 30 days forward – the result is the deadline with its day of the week. A 2-year warranty: add 730–731 days (leap years are accounted for automatically) to the purchase date. A vacation starting 14 days after the notice period: base date plus 14 days forward.

Anniversaries and round dates

The “Back” mode answers questions like “what date was it 1000 days ago?” or “when was our 500th day together?”. Enter today’s date, set 1000 days and the direction “back” – the calculator shows the date and the day of the week. It is also useful for checking insurance periods, probation terms and dates in archive documents.

This calculation is for information only. Legally significant terms are defined by the legislation of your country.