Day of the Week Calculator
Find the day of the week for any date.
Day of the Week Calculator
Day of the Week Calculator
Everything you need to know
About the Day of the Week Calculator
Have you ever wondered what day of the week you were born on? Or what day Christmas falls on next year? Or what day of the week a historical event occurred? Our day of the week calculator instantly tells you the weekday for any date in the Gregorian calendar.
Common uses:
- Find your birth day of the week
- Plan future events and holidays
- Verify historical dates
- Calculate recurring annual events
- Solve calendar puzzles
How It Works
The calculator uses Zeller's Congruence or similar algorithms to determine the day of the week mathematically. These formulas account for:
- The year (including century rules)
- The month
- The day of the month
- Leap year adjustments
Zeller's Congruence Formula
For the Gregorian calendar:
h = (q + ⌊13(m+1)/5⌋ + K + ⌊K/4⌋ + ⌊J/4⌋ - 2J) mod 7
Where:
- h = day of week (0=Saturday, 1=Sunday, 2=Monday... 6=Friday)
- q = day of month
- m = month (3=March, 4=April... 14=February)
- K = year of century (year mod 100)
- J = zero-based century (⌊year/100⌋)
Note: January and February are counted as months 13 and 14 of the previous year.
Interesting Day of the Week Facts
The 13th Falls More Often on Friday
Over a 400-year Gregorian cycle:
- Friday the 13th occurs 688 times
- Sunday and Wednesday the 13th occur 687 times
- Monday and Tuesday the 13th occur 685 times
- Thursday and Saturday the 13th occur 684 times
Friday is slightly more likely to be the 13th!
Birth Day Distribution
In a typical year, some days occur 52 times and one day occurs 53 times:
- In non-leap years: 53 of whichever day January 1 falls on
- In leap years: 53 of the day January 1 falls on AND 53 of the day January 2 falls on
If you were born on a Wednesday, there are more Wednesdays in most years.
The Gregorian Calendar Repeats
The Gregorian calendar repeats every 400 years (or 28 years within a century for most purposes). This means:
- April 15, 2026 is a Wednesday
- April 15, 2426 will also be a Wednesday
Famous Historical Dates
| Event | Date | Day of Week |
|---|---|---|
| Declaration of Independence signed | July 4, 1776 | Thursday |
| Abraham Lincoln assassinated | April 14, 1865 | Friday |
| Wright Brothers first flight | December 17, 1903 | Thursday |
| Titanic sank | April 15, 1912 | Monday |
| World War I armistice | November 11, 1918 | Monday |
| Stock market crash (Black Tuesday) | October 29, 1929 | Tuesday |
| Pearl Harbor attack | December 7, 1941 | Sunday |
| D-Day (Normandy landings) | June 6, 1944 | Tuesday |
| Moon landing | July 20, 1969 | Sunday |
| Fall of Berlin Wall | November 9, 1989 | Thursday |
| 9/11 attacks | September 11, 2001 | Tuesday |
| iPhone released | June 29, 2007 | Friday |
Planning Annual Events
If you know what day a date falls on this year, you can predict next year:
| This Year's Day | Next Year's Day (Non-Leap) | Next Year's Day (Leap) |
|---|---|---|
| Monday | Tuesday | Tuesday |
| Tuesday | Wednesday | Wednesday |
| Wednesday | Thursday | Thursday |
| Thursday | Friday | Friday |
| Friday | Saturday | Saturday |
| Saturday | Sunday | Sunday |
| Sunday | Monday | Monday |
In a leap year, dates after February 29 shift by two days instead of one.
Birthstones and Birth Flowers by Month
| Month | Birthstone | Birth Flower |
|---|---|---|
| January | Garnet | Carnation |
| February | Amethyst | Violet |
| March | Aquamarine | Daffodil |
| April | Diamond | Daisy |
| May | Emerald | Lily of the Valley |
| June | Pearl/Alexandrite | Rose |
| July | Ruby | Larkspur |
| August | Peridot | Gladiolus |
| September | Sapphire | Aster |
| October | Opal/Tourmaline | Marigold |
| November | Topaz/Citrine | Chrysanthemum |
| December | Turquoise/Zircon | Narcissus |
Zodiac Signs by Date
| Sign | Dates | Element |
|---|---|---|
| Capricorn | Dec 22 - Jan 19 | Earth |
| Aquarius | Jan 20 - Feb 18 | Air |
| Pisces | Feb 19 - Mar 20 | Water |
| Aries | Mar 21 - Apr 19 | Fire |
| Taurus | Apr 20 - May 20 | Earth |
| Gemini | May 21 - Jun 20 | Air |
| Cancer | Jun 21 - Jul 22 | Water |
| Leo | Jul 23 - Aug 22 | Fire |
| Virgo | Aug 23 - Sep 22 | Earth |
| Libra | Sep 23 - Oct 22 | Air |
| Scorpio | Oct 23 - Nov 21 | Water |
| Sagittarius | Nov 22 - Dec 21 | Fire |
Frequently Asked Questions
What day of the week was I born on?
Enter your birth date in the calculator to find out. Many people find their "birth day" becomes a lucky day for them.
Why does the day of the week change each year?
A normal year has 365 days = 52 weeks + 1 day. So each date shifts forward by one weekday. Leap years add an extra day, causing a two-day shift for dates after February 29.
Can I calculate the day for dates before 1752?
The calculator uses the Gregorian calendar. For dates before your country's adoption of the Gregorian calendar (1752 for Britain and colonies, 1582 for most of Europe), results may differ from historical records.
What's the most common birthday in the US?
September 9 is statistically the most common birthday in the United States, followed by September 19 and September 12.
How do I find the day of the week without a calculator?
Memorize the doomsday for the year, then use known anchor dates (4/4, 6/6, 8/8, 10/10, 12/12 all fall on the same day—the "doomsday"). This is John Conway's Doomsday Algorithm.