Date & time
Date calculator
Add or subtract days, weeks, months, and years from a chosen calendar date.
Calculators / Date & time / Day of the week
Day of the week calculator
Find the weekday for a Gregorian calendar date.
On this page
Day of weekSunday
Calculator controls
How to calculate
Find the weekday for a Gregorian calendar date.
Convert the date to a Gregorian day number and take the remainder modulo seven.
Worked example
Calendar date: 2026-09-13.
Day of week: Sunday .
Assumptions and limits
Uses the proleptic Gregorian calendar and UTC date, without local time or historical calendar changes.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Find the weekday for a Gregorian calendar date. The displayed figures use the inputs and formula shown on this page.
When this tool is useful
Use the day of the week to compare a scenario, check an estimate, or verify a manual calculation.
Understanding your inputs
| Input | What to enter |
|---|---|
| Calendar date | Enter the value in the format shown. |
Frequently asked questions
What should I check before using the day of the week result?
Uses the proleptic Gregorian calendar and UTC date, without local time or historical calendar changes.
Is this day of the week result exact?
It is exact for the stated mathematical model and entered values. Real-world results can differ when rates, timing, fees, definitions or measurement conditions differ.