If you know what day January 1 fell on in your birth year, you can count forward to your birthday. The table below shows January 1 for years 1950–2010:
Lookup table: what day was January 1 in your birth year?
| Year | Jan 1 day | Year | Jan 1 day | Year | Jan 1 day |
|---|---|---|---|---|---|
| 1950 | Sunday | 1970 | Thursday | 1990 | Monday |
| 1952 | Tuesday | 1972 | Saturday | 1992 | Wednesday |
| 1954 | Friday | 1974 | Tuesday | 1994 | Saturday |
| 1956 | Sunday | 1976 | Thursday | 1996 | Monday |
| 1958 | Wednesday | 1978 | Sunday | 1998 | Thursday |
| 1960 | Friday | 1980 | Tuesday | 2000 | Saturday |
| 1962 | Monday | 1982 | Friday | 2002 | Tuesday |
| 1964 | Wednesday | 1984 | Sunday | 2004 | Thursday |
| 1966 | Saturday | 1986 | Wednesday | 2006 | Sunday |
| 1968 | Monday | 1988 | Friday | 2008 | Tuesday |
How to calculate it by hand
You can calculate the day of any date using this formula:
- Take the last two digits of the year: y
- Add: y + ⌊y/4⌋ + day + month_code + century_code
- Take the result mod 7: 0=Sun, 1=Mon, 2=Tue, 3=Wed, 4=Thu, 5=Fri, 6=Sat
Month codes: Jan=1, Feb=4, Mar=4, Apr=0, May=2, Jun=5, Jul=0, Aug=3, Sep=6, Oct=1, Nov=4, Dec=6 (January/February use previous year). Century codes: 1900s=0, 2000s=6.
Example: What day was July 20, 1969?
y=69, ⌊69/4⌋=17, day=20, month_code(Jul)=0, century(1900s)=0
69+17+20+0+0 = 106 → 106 mod 7 = 0 = Sunday ✓
Fun facts about birth days
Statistically, births are not evenly distributed across days of the week:
- Tuesday and Wednesday have the most births (scheduled C-sections and inductions)
- Saturday and Sunday have the fewest (fewer elective procedures on weekends)
- Natural (unscheduled) births are roughly equal across all 7 days
FAQ
What day of the week was I born if I was born on January 1, 2000?
January 1, 2000 was a Saturday.
What day of the week was I born if I was born on July 4, 1990?
July 4, 1990 was a Wednesday.
What day of the week was I born if I was born on December 25, 1985?
December 25, 1985 was a Wednesday.
Is there an app that tells me what day I was born?
Yes — use the "What day is it?" calculator on this site. Enter any date and it instantly returns the day of the week, including historical dates.
What is the most common birth day of the week?
Tuesday is typically the most common birth day in countries with many hospital-scheduled births, followed closely by Wednesday. Saturday and Sunday are the least common.