Date Calculator
Time Between Dates · Add/Subtract Days · Working Days · Age Calculator · Day of Week · Countdown
Time Between Two Dates
Add or Subtract Days to a Date
Working Days Calculator
Age Calculator
Countdown to Event
Day of the Week Finder
About Calendars and Date Systems
Dates and calendars are central to human society for tracking time, planning, and synchronizing activities. The Gregorian calendar is the most widely used internationally, but other civil and religious calendars (such as the Islamic, Hebrew, Chinese, and Hindu calendars) are still in use.
- Leap years help synchronize the solar year (365.24 days) with the calendar year—February 29th appears in leap years.
- Business/working days typically exclude weekends (Saturday & Sunday) and national holidays, but this may vary by region and industry.
- Week begins on Monday in most countries, but in the U.S., Sunday is often considered the first day.
- Some countries use different fiscal calendars and public holidays, affecting business day calculations.
- Day of week determination: The Gregorian calendar repeats every 400 years, making calculation of weekdays for historical dates reliable.
For a deeper look at global date systems, see resources from the Wikipedia List of Calendars.