How the dates are calculated
Every date on this site is calculated by a program from published rules, then compared with official tables before the pages are built. This page lists the rules, the sources and the checks.
The 11 federal holidays
The list comes from 5 U.S.C. §6103(a), which opens with the words The following are legal public holidays
and then names them. Each holiday is either a fixed date or a weekday counted within a month. The rule column below uses the wording of the law.
| Holiday | Rule in §6103(a) |
|---|---|
| New Year's Day | January 1 |
| Birthday of Martin Luther King, Jr. | the third Monday in January |
| Washington's Birthday | the third Monday in February |
| Memorial Day | the last Monday in May |
| Juneteenth National Independence Day | June 19 |
| Independence Day | July 4 |
| Labor Day | the first Monday in September |
| Columbus Day | the second Monday in October |
| Veterans Day | November 11 |
| Thanksgiving Day | the fourth Thursday in November |
| Christmas Day | December 25 |
Two rules are easy to get wrong. Thanksgiving is the fourth Thursday in November, which is not always the last one: in 2029 it is Nov 22, 2029, and November 29 is a fifth Thursday. Memorial Day is the last Monday in May, which can be the fourth or the fifth (May 25, 2026 and May 31, 2027).
Weekend days off
Five of the holidays have fixed dates and can fall on a weekend. For federal employees whose workweek is Monday to Friday:
- Saturday → the Friday before, under §6103(b).
- Sunday → the Monday after, under Executive Order 11582, Sec. 3(a), which is printed in the notes to §6103.
The day off can land in a different year. New Year's Day 2028 falls on Saturday, January 1, 2028, so it is observed on Friday, December 31, 2027. The calendars show it in December 2027 and count it among 2027's days off.
Inauguration Day, January 20 every fourth year after 1965, is a holiday only for federal employees in and around Washington, D.C. (§6103(c)). It is not shown on the general calendars.
Who the holidays apply to
Section 6103 sets the holidays of federal employees. Private employers, schools, banks, markets and state governments make their own lists. Many of them match the federal one, but not all, so the calendars mark these days as federal holidays and nothing more.
Sunday or Monday first, and ISO weeks
Each month can be shown with Sunday or Monday as the first column. The program places the 1st of the month in the right column for either layout, so a month can need four, five or six rows. February 2027 starts on a Monday, so it fills exactly four rows in the Monday layout.
Week numbers follow ISO 8601: weeks run Monday to Sunday, and week 1 is the one that contains the first Thursday of the year. That is why Friday, January 1, 2027 belongs to week 53 of 2026. Some US schedules count weeks from January 1 or from Sunday, which can give a different number. See the week number page.
Three things called a Julian date
- Day of the year: January 1 is day 1, and December 31 is day 365, or day 366 in a leap year. Date codes on some food packaging and military supplies use it. Monday, March 1, 2027 is day 60.
- YYDDD code: the last two digits of the year followed by the three-digit day of the year, so Mar 1, 2027 is 27060. Some systems use four year digits instead (YYYYDDD).
- Julian Day Number: the count of days used in astronomy, starting from a day in 4713 BC on the Julian calendar. Jan 1, 2000 is day 2451545. The number belongs to the day that begins at noon UTC on that date.
The Julian date today page shows all three for the current day, and the converter has charts for the first two and a table for the third.
Leap years
A year is a leap year if it divides by 4, except years that divide by 100, unless they also divide by 400. So 2000 was a leap year, while 1900 was not and 2100 will not be. 2026 is not a leap year; 2027 is not a leap year; 2028 is one.
How the results are checked
Before the site is built, a test suite runs and the build stops if any test fails. It includes:
- Cases that are easy to get wrong: Washington's Birthday 2027 on February 15, Thanksgiving 2029 on November 22, February 2027 in four Monday-first rows, January 1, 2027 in week 53 of 2026, and New Year's Day 2028 observed on December 31, 2027.
- The holiday names and rule wording above, and the quotations used on the holiday pages, matched word for word against a saved copy of the law.
- The federal days off we calculate for 2026 to 2028, compared row by row with the holiday tables published by the U.S. Office of Personnel Management.
- Day of the year, ISO week and Julian Day Number for every date from 1900 to 2100, compared with a separate implementation in Python's standard library. The small script that shows "today" on two pages is tested against the same rules.
Sources
- 5 U.S.C. §6103 — Holidays (United States Code, 2023 edition), U.S. Government Publishing Office (govinfo). Checked 2026-10-03.
- 36 U.S.C. §117 — Mother's Day (United States Code, 2024 edition), U.S. Government Publishing Office (govinfo). Checked 2026-10-04.
- 36 U.S.C. §109 — Father's Day (United States Code, 2024 edition), U.S. Government Publishing Office (govinfo). Checked 2026-10-04.
- Federal Holidays (pay & leave), U.S. Office of Personnel Management. Checked 2026-10-04.
These are works of the US federal government. Quotations are short and attributed.
Please note
Dates are calculated from published public rules. For work schedules, follow your employer or the official announcement.
Update log
- 2026-10-04: pages generated. Month pages show the next time each month comes round, so they move forward a year at the start of every month.
- 2026-10-04: the list in §6103(a) checked against the 2023 edition of the U.S. Code, which has 11 holidays. The most recent addition was Juneteenth National Independence Day (Pub. L. 117–17, June 17, 2021).