Day of the Week Finder
Find out what day of the week any date falls on — past or future.
How the day of week is determined
The JavaScript Date object stores dates as milliseconds since Unix epoch (Jan 1, 1970). The getDay() method returns 0 (Sunday) through 6 (Saturday) for any date.
Why knowing the day of the week matters
Quickly verify whether a chosen date falls on a weekday or weekend before booking a venue or sending invitations.
Historians and genealogists use day-of-week finders to verify records — for example, confirming a birth certificate date matches a reported day.
Many auspicious dates in Hindu and Jain calendars depend on the weekday (Somvar, Mangalwar etc.). This tool helps cross-check the Gregorian equivalent.
Frequently asked questions
What is the earliest date this tool supports?
Most modern browsers support date inputs from year 0001. However, the Gregorian calendar was introduced in October 1582, so days of the week for earlier dates are proleptic Gregorian (extrapolated backwards) and may not match Julian calendar records.
What is an ISO week number?
ISO 8601 defines weeks as starting on Monday. Week 1 is the week that contains the year's first Thursday. This means a year can have either 52 or 53 weeks, and early January dates may belong to the previous year's last week.
How does the mini calendar work?
The mini calendar shows the 7 days of the week containing your selected date, with Monday as the first column. The selected date is highlighted in green.
What does "leap year" mean?
A leap year has 366 days instead of 365. It occurs when the year is divisible by 4, except for century years which must be divisible by 400. For example, 2000 was a leap year but 1900 was not.
Can I use this for future dates?
Yes. The calculator works for any date your browser's date input accepts — past, present or future. The day of the week is mathematically deterministic and does not depend on external data.