What Day of the Week Was December 7, 1941?
December 7, 1941 (Pearl Harbor Day) was a Sunday. On the morning of December 7, 1941, Japanese forces attacked the US Pacific Fleet at Pearl Harbor, Hawaii, and the United States entered World War II the next day.
December 7, 1941 is a Sunday
- Day of the year:
- day 341 of 365, 24 days left in the year
- Week number:
- ISO week 49 of 1941 · US week 50
- Weekday number:
- 1 in the US (Sunday = 1) · 7 in ISO 8601 (Monday = 1)
Another date? Change the date above, or open the day of the week calculator for today's weekday and any other date.
December 7, 1941 in numbers
| December 7, 1941 | |
|---|---|
| Day of the week | Sunday |
| Weekday number | 1 in the US (Sunday = 1), 7 in ISO 8601 (Monday = 1) |
| Day of the year | 341 of 365, 24 days left |
| ISO week | Week 49 of 1941 |
| US week | Week 50 |
| Leap year | No, 1941 had 365 days |
| Julian Day Number | 2430336 |
December 1941 calendar
The whole month, with December 7, 1941 highlighted. The column on the left is the US week number.
| Wk | Su | Mo | Tu | We | Th | Fr | Sa |
|---|---|---|---|---|---|---|---|
| 49 | 1 | 2 | 3 | 4 | 5 | 6 | |
| 50 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |
| 51 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| 52 | 21 | 22 | 23 | 24 | 25 | 26 | 27 |
| 53 | 28 | 29 | 30 | 31 |
The years 1902, 1913, 1919, 1930, 1947, 1958, 1969, 1975 have the same calendar as 1941: they start on the same weekday and are common years too, so December 7 is a Sunday in each of them.
How to work out that December 7, 1941 was a Sunday
Zeller's congruence gives the weekday of any Gregorian date with a few sums:
- Day q = 7; month m = 12.
- Year of the century K = 41; century J = 19.
- q + ⌊13 × (m + 1) ÷ 5⌋ + K + ⌊K ÷ 4⌋ + ⌊J ÷ 4⌋ + 5 × J = 7 + 33 + 41 + 10 + 4 + 95 = 190.
- 190 divided by 7 leaves 1, and 1 stands for Sunday (0 is Saturday, 1 Sunday, up to 6 for Friday).
DateMath's calculator gets the same answer another way, by counting the days from a fixed date and taking the remainder after whole weeks.
What day of the week is December 7 in the coming years?
| Date | Weekday | Since 1941 |
|---|---|---|
| December 7, 2027 | Tuesday | 86 years |
| December 7, 2028 | Thursday | 87 years |
| December 7, 2029 | Friday | 88 years |
| December 7, 2030 | Saturday | 89 years |
| December 7, 2031 | Sunday | 90 years |
| December 7, 2032 | Tuesday | 91 years |
| December 7, 2033 | Wednesday | 92 years |
| December 7, 2034 | Thursday | 93 years |
| December 7, 2035 | Friday | 94 years |
| December 7, 2036 | Sunday | 95 years |
How DateMath finds the day of the week
DateMath counts the days from a fixed date to yours in the Gregorian calendar and takes the remainder after whole weeks, so every date in the years 1 to 9999 gets its weekday, leap days included. The same date is then numbered both ways: in the US, Sunday is day 1 of the week; in ISO 8601, Monday is day 1 and Sunday day 7. Today and tomorrow come from your device's date.
- The Gregorian calendar. DateMath treats every date as a Gregorian date, with its leap-year rule: a year divisible by 4 is a leap year, except century years not divisible by 400, so 2000 had a February 29 and 2100 will not. Source: Gregorian calendar.
- ISO 8601 week dates. DateMath numbers weeks by ISO 8601: weeks start on Monday, week 1 is the week with the year's first Thursday, and a year has 52 or 53 weeks. Source: ISO 8601.
DateMath's date math is tested against more than 100 cases worked out by hand. Every worked example and table on the site is computed with the same code the calculators run, so a page and its calculator can't disagree.
Frequently asked questions
- What day of the week was December 7, 1941 (Pearl Harbor Day)?
- December 7, 1941 was a Sunday. It was day 341 of 1941, in ISO week 49 and US week 50.
- What day of the week was Pearl Harbor attacked?
- On a Sunday morning in Hawaii. In Japan, across the International Date Line, it was already Monday, December 8. President Roosevelt called it "a date which will live in infamy" in his address to Congress on Monday, December 8.
- What day of the week is December 7 in 2027?
- December 7, 2027 is a Tuesday. A date moves one weekday later each year, and two after a February 29.
- Was 1941 a leap year?
- No. 1941 had 365 days, so December 7, 1941 was day 341 of 365, with 24 days left in the year.