DateMath

What Day of the Week Was July 20, 1969?

July 20, 1969 (the Moon landing) was a Sunday. On July 20, 1969, Apollo 11's lunar module Eagle landed on the Moon, and that night, US time, Neil Armstrong and Buzz Aldrin became the first people to walk on its surface. Source: NASA: Apollo 11.

July 20, 1969 is a Sunday

Day of the year:
day 201 of 365, 164 days left in the year
Week number:
ISO week 29 of 1969 · US week 30
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.

July 20, 1969 in numbers

July 20, 1969
Day of the weekSunday
Weekday number1 in the US (Sunday = 1), 7 in ISO 8601 (Monday = 1)
Day of the year201 of 365, 164 days left
ISO weekWeek 29 of 1969
US weekWeek 30
Leap yearNo, 1969 had 365 days
Julian Day Number2440423

July 1969 calendar

The whole month, with July 20, 1969 highlighted. The column on the left is the US week number.

July 1969
WkSuMoTuWeThFrSa
2712345
286789101112
2913141516171819
3020212223242526
312728293031

The years 1930, 1941, 1947, 1958, 1975, 1986, 1997, 2003 have the same calendar as 1969: they start on the same weekday and are common years too, so July 20 is a Sunday in each of them.

How to work out that July 20, 1969 was a Sunday

Zeller's congruence gives the weekday of any Gregorian date with a few sums:

  1. Day q = 20; month m = 7.
  2. Year of the century K = 69; century J = 19.
  3. q + ⌊13 × (m + 1) ÷ 5⌋ + K + ⌊K ÷ 4⌋ + ⌊J ÷ 4⌋ + 5 × J = 20 + 20 + 69 + 17 + 4 + 95 = 225.
  4. 225 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 July 20 in the coming years?

DateWeekdaySince 1969
July 20, 2027Tuesday58 years
July 20, 2028Thursday59 years
July 20, 2029Friday60 years
July 20, 2030Saturday61 years
July 20, 2031Sunday62 years
July 20, 2032Tuesday63 years
July 20, 2033Wednesday64 years
July 20, 2034Thursday65 years
July 20, 2035Friday66 years
July 20, 2036Sunday67 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 July 20, 1969 (the Moon landing)?
July 20, 1969 was a Sunday. It was day 201 of 1969, in ISO week 29 and US week 30.
Was the Moon walk on July 20 or July 21, 1969?
Both, depending on the clock. Armstrong stepped onto the Moon at 10:56 PM Eastern Time on Sunday, July 20, which was 02:56 UTC on Monday, July 21. The landing itself, a few hours earlier, was on July 20 on both clocks.
What day of the week is July 20 in 2027?
July 20, 2027 is a Tuesday. A date moves one weekday later each year, and two after a February 29.
Was 1969 a leap year?
No. 1969 had 365 days, so July 20, 1969 was day 201 of 365, with 164 days left in the year.

More dates in history