🗓️ Day of the Week Calculator
Enter any date and instantly see which day of the week it is (or was), whether it’s a weekend, and how many days from today.
Monday
Weekday · ISO day 1 of 7 · that’s today
Day names use the proleptic Gregorian calendar. ISO numbering: Monday = 1 … Sunday = 7. 🔒 Computed in your browser.
How the day of the week calculator works
The tool determines the weekday for your date using the proleptic Gregorian calendar, reports whether it’s a weekend (Saturday or Sunday), gives the ISO weekday number (Monday = 1 through Sunday = 7), and — comparing against today — tells you whether it’s in the past or future and by how many days.
Knowing the weekday of a date is handy for planning events and deadlines, checking a historical or future date, or settling the “what day was I born?” question. The ISO weekday number (Monday = 1) is the convention used by spreadsheets and many programming libraries, which differs from the US convention of Sunday as the first day. It all runs locally in your browser.
Frequently asked questions
What day of the week was a given date?
Enter the date and the tool shows the weekday — for example January 1, 2000 was a Saturday. It works for past and future dates alike.
Which day is day 1 of the week?
This tool reports the ISO weekday number, where Monday = 1 and Sunday = 7 — the convention used by ISO 8601, spreadsheets and most programming libraries. Some US calendars instead treat Sunday as the first day.
Does it tell me if a date is a weekend?
Yes — it flags Saturday and Sunday as weekend days, which is useful when planning deadlines or deliveries that only count working days.
Is it accurate for very old or far-future dates?
It uses the proleptic Gregorian calendar (today’s calendar projected backward and forward), which is the standard for date arithmetic. Historical dates that were recorded under the Julian calendar may differ.
Is my date uploaded?
No — the weekday is computed entirely in your browser and the tool works offline.