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How to Use the Day Counter

To find the days between two dates, select a start and end date. Check the "include end day" box if the final day should be part of the count. The calculator will return the total number of days and can optionally break down the count into weekdays and weekend days.

The Doomsday Rule

The day of the week for any given date can be calculated using algorithms like the Doomsday rule, developed by John Conway. This method relies on identifying that for any year, certain easy-to-remember dates all fall on the same day of the week—this day is called the "doomsday."

For example, 4/4, 6/6, 8/8, 10/10, and 12/12 are always doomsdays. Once the doomsday for the year is known, any other date can be calculated by finding the number of days it is before or after a known doomsday.