What Is a Day of Week Calculator?
A Day of Week Calculator finds which weekday corresponds to
a specific calendar date. Simply enter a date and the tool
determines whether it falls on Monday, Tuesday, Wednesday,
Thursday, Friday, Saturday, or Sunday.
In addition to the weekday name, this calculator provides
useful calendar information such as the ISO week number,
day of the year, quarter, month length, and leap year status.
Quick Example:
If you enter a particular birthday, anniversary, historical
date, or future event date, the calculator instantly identifies
which day of the week corresponds to it.
How to Use the Day of Week Calculator
You can find the weekday of almost any supported calendar date
in three simple steps.
1
Choose Your Date
Select the month, day, and year using the calendar date field.
2
Calculate the Day
Click Calculate Day and the tool will process the selected date.
3
View Full Details
See the day name, week number, day of year, quarter,
leap year status, and more.
The Seven Days of the Week
The modern week contains seven days. For this calculator,
Monday is treated as day 1 and Sunday as day 7 when displaying
the day number.
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Understanding Your Day of Week Results
ISO Week Number
Shows which numbered ISO week of the year contains
your selected date.
Day of Year
Shows the position of the date within its year,
starting with January 1 as day 1.
Calendar Quarter
Identifies whether the selected date falls in
Q1, Q2, Q3, or Q4.
Day Number of Week
The calculator uses Monday as day 1 and continues sequentially
through Sunday as day 7.
Day of Year
The day of year shows how many calendar days have been reached
within the selected year. December 31 is day 365 in a normal
year and day 366 in a leap year.
Quarter of Year
A calendar year is divided into four quarters. January through
March form Q1, April through June form Q2, July through September
form Q3, and October through December form Q4.
Why Use a Day of Week Calculator?
Knowing the exact weekday of a date can be helpful for personal,
business, educational, and historical purposes.
-
Find which day of the week you were born.
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Check the weekday of an anniversary.
-
Identify the weekday of historical events.
-
Plan future meetings and appointments.
-
Verify dates in records and documents.
-
Check whether a date falls on a weekend.
-
Find ISO week numbers for reporting.
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Determine the calendar quarter for a date.
How Leap Years Affect Calendar Dates
Most calendar years contain 365 days. A leap year contains
366 days because an additional date, February 29, is added
to the calendar.
This additional day affects the weekday progression for dates
later in the year and is important when calculating historical
or future weekdays accurately.
Leap Year Rule:
A year is a leap year when it is divisible by 4, except for
century years. A century year must also be divisible by 400
to qualify as a leap year.
Frequently Asked Questions
What is a Day of Week Calculator?
It is a date tool that determines which weekday corresponds
to a specific calendar date.
Can I calculate the day of a past date?
Yes. Select a supported historical date and the calculator
will identify its day of the week.
Can I check future dates?
Yes. The calculator works with supported future dates as well
as current and past dates.
What is the ISO week number?
The ISO week number identifies the numbered week containing
the selected date under the ISO week-date system.
What does day of year mean?
Day of year represents the selected date's numerical position
within its calendar year. January 1 is day 1.
What does Q1, Q2, Q3, or Q4 mean?
These represent the four calendar quarters of a year. Each
quarter contains three consecutive months.
Does the calculator detect leap years?
Yes. The result automatically shows whether the selected
year is a leap year.
Does Saturday count as a weekday?
Under the common Monday-to-Friday convention, Saturday and
Sunday are weekend days. Actual working-week conventions can
vary by location and organization.