Days and weekdays on a calendar

Calendar days, weekdays, and the ISO week

The day count is calendar days. The weekday count is a separate number. A shift uses years, then months, then days. A clock-time span with a break belongs on the hours calculator. A birth date belongs on the age calculator.

The day count and the weekday count

Enter a start date and an end date, then press Calculate. Today beside a field fills that field with this device's local date. Swap exchanges the two dates. Reset returns both fields to today. The same date is 0 days. The next day is 1 day. An earlier end date is a negative day count. From 1 January 2025 to 3 February 2026 is 1 year, 1 month, and 2 days. The weekday count includes both dates and leaves out Saturday and Sunday.

Years, months, and days only

Choose a base date, choose Add or Subtract, then enter years, months, and days. There is no week field. Press Calculate. Years are applied first, then months, then days. A blank field counts as zero.

Month-end, leap day, and the ISO week

• A month shift keeps the day number when that month has it. Otherwise the result is the last day of the month. 31 January plus 1 month is 28 February, or 29 February in a leap year.
• 29 February plus 1 year becomes 28 February when the following year is not a leap year. 31 March minus 1 month is 28 February, or 29 February in a leap year.
• Adding days rolls into the next month and the next year. 31 January plus 1 day is 1 February. The ISO week starts on Monday, and week 1 contains the first Thursday. The week-year can differ from the calendar year.

A deadline on the calendar

• Read the weekday count before a hand-in date. A live countdown keeps updating until the date and time, and it does not ring at zero.
• Move a known date by several months or years when you need the resulting calendar date.
• Check a leap day, a month-end date, or which ISO week a date falls in before you plan around it.

What the counts leave out

• Counts use calendar dates. The length of a local day is ignored, so daylight saving time does not change the day count.
• Hours and minutes are not part of this calculator, and neither is a week field.
• Accepted years are 1 through 9999. A result outside that range is rejected.
• The weekday count is separate from the calendar-day count. Saturday and Sunday are excluded. Public holidays are not excluded. Both the start date and the end date stay included.
• The dates you type stay on the open page. This browser does not keep them.
• Today on this device is filled in after the page opens. It is not written into the page file.

Questions about days and weekdays

Related tools

• Countdown
• Clock
• Age calculator
• Hours calculator