Day of the Week Calculator

For the Gregorian calendar:

Where:

• h is the day of week (0=Saturday, 1=Sunday, 2=Monday, ..., 6=Friday)
• q is the day of month
• m is the month (3=March, 4=April, ..., 14=February)
• K is the year of the century (year mod 100)
• J is the zero-based century (year div 100)

January and February are counted as months 13 and 14 of the previous year.

What day was 15 August 1947?

1. q = 15, m = 8, year = 1947
2. K = 47, J = 19
3. h = (15 + ⌊13×9/5⌋ + 47 + ⌊47/4⌋ + ⌊19/4⌋ - 2×19) mod 7
4. h = (15 + 23 + 47 + 11 + 4 - 38) mod 7 = 62 mod 7 = 6
5. 6 = Friday

Result: Friday

1. Enter the date
2. Click "Calculate" to see the day of the week

| Date | Day of Week | |------|-------------| | 1 Jan 2025 | Wednesday | | 1 Jan 2026 | Thursday | | 1 Jan 2027 | Friday | | 1 Jan 2028 | Saturday | | 1 Jan 2029 | Monday | | 1 Jan 2030 | Tuesday |

For 2000-2099:

1. Take the last two digits of the year
2. Add the number of leap years (divide by 4)
3. Add the day of the month
4. Add a month code (Jan=0, Feb=3, Mar=3, Apr=6, May=1, Jun=4, Jul=6, Aug=2, Sep=5, Oct=0, Nov=3, Dec=5)
5. Divide by 7 and take the remainder
6. Match to day (0=Sunday, 1=Monday, ..., 6=Saturday)

• Historical research
• Birth date verification
• Legal and contractual date verification
• Event planning
• Genealogy research

What day was the first Moon landing? 20 July 1969 was a Sunday.

When was the first computer? The ENIAC was unveiled on 15 February 1946, a Thursday.

Can I find my birth day? Yes, enter your birth date to see what day of the week you were born.

How do I calculate tomorrow's day? Add 1 to today's day number (wrapping from Sunday to Monday).

Is there a pattern? Each non-leap year shifts days by 1 (365 mod 7 = 1), leap years shift by 2.