Enter a date to see its weekday. For example, 15 September 2026 is a Tuesday, 4 July 2026 is a Saturday and 25 December 2026 is a Friday. The tool uses the Gregorian calendar for every date. That matches today’s calendar, but it does not match old records written before a country switched: Catholic Europe switched in October 1582, and Britain and its colonies in September 1752.
After you know the weekday, you can also measure the days between two dates with the date difference calculator.
This day of the week calculator returns the weekday name for a Gregorian calendar date. The sample date 2026-09-15 falls on Tuesday.
Use it for scheduling, history homework, and quick checks when a paper calendar is not nearby. To move a date forward or back first, see adding or subtracting days from a date. Pregnancy timing questions belong on health tools such as the due date calculator rather than a weekday namer.
2026 dates and their weekdays
| Date | Weekday |
|---|---|
| 4 Jul 2026 | Saturday |
| 15 Sep 2026 | Tuesday |
| 26 Nov 2026 (US Thanksgiving) | Thursday |
| 25 Dec 2026 | Friday |
| 1 Jan 2027 | Friday |
| 1 Jan 2000 | Saturday |
| 20 Jul 1969 (Moon landing) | Sunday |
How the formula works
Gregorian weekday algorithms combine year, month, and day with leap year adjustments so each civil date maps to one of seven weekday names. The calculator applies that mapping and prints the English weekday.
Worked example
Enter 2026-09-15. The Gregorian weekday for that date is Tuesday. Any trustworthy civil calendar for September 2026 should show the same name.
| Input | Value |
|---|---|
| Date | 2026-09-15 |
| Calendar | Gregorian |
| Weekday | Tuesday |
How to use the fields
- Enter year, month, and day as YYYY-MM-DD (for example 2026-09-15), so month and day cannot be swapped.
- Run the calculation.
- Read the weekday name and cross check against a calendar if the event is critical.
Leap years and month lengths
February 29 exists only in leap years. Invalid dates should be rejected. September always has 30 days, so 2026-09-15 is a valid mid month sample. September has 30 days, so day 31 is invalid and should never produce a weekday. Always validate the calendar date before trusting a name.
Leap years and the calendar switch
| Rule or event | Detail |
|---|---|
| Leap year | Divisible by 4, except century years, which must be divisible by 400. 2000 and 2028 are leap years; 1900, 2026 and 2100 are not. |
| Gregorian switch (1582) | Thursday 4 October 1582 was followed by Friday 15 October 1582. |
| Britain and colonies (1752) | 2 September 1752 was followed by Thursday 14 September 1752. |
Sources: https://aa.usno.navy.mil/faq/leap_years and https://www.legislation.gov.uk/apgb/Geo2/24/23. The weekdays come from Python’s proleptic Gregorian calendar.
Common mistakes
- Swapping month and day in locales that write day first
- Using a Julian historical date without conversion
- Expecting the tool to list holidays or store hours
- Confusing weekday name with week number of the year
Historical caution
Records before a region adopted the Gregorian calendar can disagree with modern weekday calculators. For school history projects, confirm which calendar the source used. Old dates on cornerstones and title pages are often written in Roman numerals, so decode them first with the roman numeral converter. The table above shows the two best-known switches.
Limitations
Gregorian civil weekday naming only. No holiday database, no Julian historical mode, and no meeting availability engine.