How to use
- Enter a date. It starts as today.
- Read the day of the week.
- Check the extras: which occurrence of that weekday it is in the month, the day of the year, the week number and whether it’s a leap year.
- The table shows the same date in nearby years.
How the weekday is calculated
weekday = (days since 1 January 1970 + 4) mod 7
0 = Sunday, 1 = Monday … 6 = Saturday
- 1 January 1970 was a Thursday (weekday 4), so counting the days from it and taking the remainder after dividing by 7 gives the weekday.
- Leap years follow the Gregorian rule: every 4 years, except century years not divisible by 400.
Example
21 October 2026:
- It is 20,747 days after 1 January 1970.
- (20,747 + 4) mod 7 = 3, which is Wednesday.
- It is also day 294 of 2026 and the 3rd Wednesday of October.
1 January 2000 was a Saturday.
1 January in coming years
| Year | 1 January | Leap year? |
|---|---|---|
| 2026 | Thursday | No |
| 2027 | Friday | No |
| 2028 | Saturday | Yes |
| 2029 | Monday | No |
| 2030 | Tuesday | No |
| 2031 | Wednesday | No |
| 2032 | Thursday | Yes |
A date moves on one weekday each year, and two after a 29 February: 365 days is 52 weeks and 1 day.
Old dates and the Julian calendar
The calculator uses today’s Gregorian calendar for every date, even before it was introduced.
Britain and its colonies switched from the Julian calendar in 1752. By law, the day after 2 September 1752 became 14 September. The weekdays carried on as normal: Wednesday was followed by Thursday.
So a date in an older British record may fall on a different weekday here.
Want the week number too? Use the week number calculator. To find out how old someone is, use the age calculator.