Day of the Week Calculator
Find the day name, week number, quarter, and more for any date
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Date
Quick Facts — Days of the Week
• Monday to Friday = weekdays (5 days)
• Saturday & Sunday = weekend (2 days)
• A standard year has 52 weeks + 1 day
• A leap year has 52 weeks + 2 days
• January 1 shifts forward by 1–2 days each year
Day of the Week
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Day Type—
Day of Year—
ISO Week Number—
Quarter—
Distance from Today—
How Days of the Week Work
The Gregorian calendar repeats its day pattern every 400 years. The easiest algorithm for finding the day of the week is Zeller's congruence or Tomohiko Sakamoto's algorithm — JavaScript's Date.getDay() handles this automatically, returning 0 (Sunday) through 6 (Saturday).
Common uses: checking if a date is a working day, planning events on specific weekdays, calculating business deadlines, or just finding out what day a famous historical date fell on.
lightbulb Historic Dates
1India Independence: 15 Aug 1947 → Friday
2Gandhi Jayanti: 2 Oct 1869 → Saturday
3Moon landing: 20 Jul 1969 → Sunday
✓ New Year 2000: 1 Jan 2000 → Saturday
quizFrequently Asked Questions
What day of the week was I born?
Enter your birth date in the calculator and it will tell you instantly. The day of the week shifts by 1 each year (2 after a leap year), so it cycles every 28 years. Many people are surprised to find they were born on a Monday or a Sunday — the day is easily forgotten but historically recorded on birth certificates.
How is the day of the week calculated mathematically?
The most common algorithm is Zeller's congruence, which uses the month, day, and year with a modular arithmetic formula to determine the day. The formula accounts for century corrections in the Gregorian calendar. January 1, 2000 was a Saturday — and from there, the pattern repeats with a predictable cycle.
Why might historical dates before 1582 show different days?
In October 1582, Pope Gregory XIII introduced the Gregorian calendar, skipping 10 days (October 4 was followed by October 15). This calculator uses the proleptic Gregorian calendar for dates before 1582, which may not match historical Julian calendar records. For most modern use cases (birthdays, anniversaries), this doesn't matter.