How to use the weekday on a day of the month finder
- Enter the day of the month, such as 13.
- Choose the weekday, such as Friday.
- Enter the first year and the last year of the range, up to 200 years.
- Read the number of matches, the first and last, the table by year and the gaps between matches. Download every date as CSV.
Formula
for each month in the range with at least D days: match if the weekday of day D equals the chosen weekday
weekday of a date = (day count + 4) mod 7, with 0 = Sunday
gap = days between two consecutive matches
Months that are too short for the day number are skipped, so there is no 31st of April or 30th of February.
Friday the 13th from 2026 to 2035
Between 2026 and 2035 the 13th falls on a Friday 17 times. The first is February 13, 2026 and the last is July 13, 2035. Every one of the 10 years has at least one, and 2026 has the most, three: February, March and November. The shortest gap between two is 28 days, from February 13 to March 13, 2026, and the longest is 427 days.
For Sunday the 31st over 2026 to 2040, only months with 31 days count. The page finds 14 matches in 12 of the 15 years, with a shortest gap of 245 days.
Why every year has one
In the Gregorian calendar, every year has at least one Friday the 13th and at most three. The weekday of the 13th moves forward each month by the length of the month before, taken after removing whole weeks. A year can start on any of seven weekdays and can be a leap year or not, which makes 14 possible calendars, and each of the 14 has at least one month whose 13th is a Friday and none has more than three. A Friday the 13th in February is followed by one in March unless the year is a leap year.
The calendar repeats every 400 years, so the pattern for 2026 to 2035 will come back in 2426 to 2435. Over a full 400 years, the 13th falls on a Friday slightly more often than on any other weekday.
Other date patterns
To find dates such as the third Monday of a month, use the Nth Weekday Calculator. To check the weekday of one date, use the Day of the Week Calculator, and to list repeating dates for a schedule, use the Date Sequence Generator.
Assumptions and limits
- The Gregorian calendar is used for every year in the range, including years before 1582.
- The range is 1000 to 9999 and at most 200 years long.
- Only whole calendar days matter, with no time zones.
- The day, weekday and years shown when the page opens are examples.
Frequently asked questions
Can the 13th fall on a Friday three times in a year?
Yes. It happens when a year starts on a certain weekday, as in 2026, which has Fridays on the 13th in February, March and November.
Why are there no matches for some months?
Only months with that many days are checked. Asking for the 31st skips months with 30 days or fewer, and the 30th skips February.
What is the weekday rule?
It counts days from a fixed reference date and takes the remainder after dividing by 7. The page checks it against every date in the tests.
Does the pattern repeat?
Every 400 years exactly, because 400 years contain a whole number of weeks (20,871 weeks).