📆Day of the Week Calculator
Find the day of the week for any date in history or the future. Also shows the day of the year, ISO week number, quarter, zodiac sign, Julian Day Number, days until end of year, and whether it is a weekday or weekend.
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Day of the Week
Saturday
Days Elapsed and Remaining in Year
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Day of the Week Calculator: Find What Day Any Date Falls On
Enter any date to find the day of the week, ISO week number, day of the year, zodiac sign, and more. July 4, 2026 falls on a Saturday. The Gregorian calendar has a 400-year cycle of exactly 97 leap years — meaning any date repeats its day of the week every 400 years.
Quick fact: January 1, 2000 was a Saturday. July 20, 1969 (moon landing) was a Sunday.
| Date | Day of week | Day of year |
|---|---|---|
| Jan 1, 2026 | Thursday | Day 1 of 365 |
| Jul 4, 2026 | Saturday | Day 185 of 365 |
| Dec 25, 2026 | Friday | Day 359 of 365 |
The day of the week follows a predictable 400-year cycle due to the Gregorian calendar's leap year rules. Every 400 years, the calendar pattern repeats exactly (because 400 years = 97 leap years + 303 common years = 146,097 days, divisible evenly by 7). This means any date's day of the week can be calculated for any year in history or the future.
ISO Week Numbers
ISO 8601 defines week 1 of any year as the week containing the first Thursday. Weeks always start on Monday. This means ISO week 1 can start as early as December 29 or as late as January 4. Years can have either 52 or 53 ISO weeks. Years that start on Thursday (like 2026) have 53 weeks. The ISO week system is widely used in manufacturing, finance, and European business contexts.
Frequently Asked Questions
What day of the week was January 1, 2000?
January 1, 2000 was a Saturday. The Y2K millennium began on a weekend. Other notable dates: July 4, 1776 (US independence) was a Thursday. December 7, 1941 (Pearl Harbor) was a Sunday. November 22, 1963 (JFK assassination) was a Friday. July 20, 1969 (Moon landing) was a Sunday. September 11, 2001 was a Tuesday.
How do you calculate the day of the week for any date?
The most common algorithm is Zeller's congruence or Tomohiko Sakamoto's algorithm. Simplified: take the year, month, and day; adjust for months January and February being in the previous year; then compute h = (q + ⌊13(m+1)/5⌋ + K + ⌊K/4⌋ + ⌊J/4⌋ − 2J) mod 7 where q=day, m=month, K=year within century, J=century. The result maps 0=Saturday through 6=Friday in Zeller's. Most programming languages use 0=Sunday through 6=Saturday. Mnemonic method: memorise anchor days for each month and count from there.
What is an ISO week number?
ISO 8601 week numbers divide the year into weeks of exactly 7 days (Mon–Sun). Week 1 is defined as the week containing the year's first Thursday, or equivalently: the week containing January 4. This means January 1 can be in week 52 or 53 of the previous year if it falls on Friday, Saturday, or Sunday. Most years have 52 weeks; years where January 1 falls on Thursday have 53 weeks. ISO week numbers are used extensively in European business, supply chain management, and manufacturing schedules.
What day of the week does a date repeat on?
Because the Gregorian calendar has a 400-year cycle of exactly 146,097 days (= 20,871 weeks), any date repeats its day of the week every 400 years. For shorter cycles: non-leap years shift the day forward by 1 (common year = 365 = 52×7+1). Leap years shift it forward by 2. As a practical shortcut: in the same year, the same calendar date one week later has the same day of week. Mnemonics like DOOMSDAY (the algorithm by John Conway) let you calculate any day mentally by remembering anchor days for each month.