Friday 13th Calculator
Every Friday the 13th in any year 1900 to 2100.
What it does
Friday the 13th lands when the thirteenth of a month hits a Friday, one to three times yearly by calendar mechanics. February starting on Sunday guarantees a Friday 13th that same month, which 2026 demonstrates.
The tool above takes any year 1900 to 2100. It returns every Friday the 13th with the count beside them.
The default 2026 holds three: February 13, March 13, and November 13. The leap year 2028 holds just one, in October, showing the full range.
Weekday math follows NIST timekeeping practice with time.gov as the public face of official US time. Gregorian rules run throughout, including century leap exceptions.
How to use
- Enter a year between 1900 and 2100.
- Read the dates first for planning (or avoiding).
- Read the count for the year trivia.
- Check neighboring years for patterns.
- Verify one date against any calendar.
Formula
- 13th
- Date tested in each of 12 months.
- Friday
- Weekday index 5 kept.
- UTC
- Zone free weekday math.
Proleptic Gregorian rules throughout without Julian reforms. Any 13th repeats Friday within 28 year cycles at most.
Worked example
Example: 2026
Default year 2026.
- Test all twelve 13ths in UTC.
- February 13 2026 is Friday.
- March 13 2026 is Friday.
- November 13 2026 is Friday; others are not.
- Tool shows Feb 13, Mar 13, Nov 13 with count 3.
Reference table
| Year | Count | Months |
|---|---|---|
| 2025 | 1 | June |
| 2026 | 3 | Feb, Mar, Nov |
| 2027 | 1 | August |
| 2028 | 1 | October |
Limits
- Gregorian calendar only throughout.
- Years 1900 to 2100; wider needs code changes.
- Superstition content free; dates are exact.
- No Julian reform modeling.
Common mistakes
- Assuming one per year always.
- Trusting memory over the calendar.
- Mixing local zones into weekday math.
- Reading Friday the 12th by off by one.
- Planning weddings around fear.
Try it yourself
Quick checks. Answers sit tucked under each question.
2027?
August 13 only: 1 Friday.
Months with most?
Three max: like Feb, Mar, Nov 2026.
Any year without?
Never. Minimum is exactly one.
Questions
How many Friday 13ths in 2026?
Three: February 13, March 13, November 13.
Can a year skip it?
No. Calendar mechanics guarantee 1 to 3 yearly.
Why February 2026?
February starts Sunday in non leap years beginning Thursday: the 13th lands Friday.
Most in one year?
Three, when February, March, and November align.
Is it unlucky?
No evidence says so; the calendar math is exact either way.
Which weekday is 13th most?
Friday tops slightly across 400 year cycles.