Date & Time Calculators
Day of the Week Calculator
Determine the day of the week, week number, and days until a specific date.
What is the Day of the Week Calculator & How does it work?
The Day of the Week Calculator uses Zeller’s Congruence to determine the day of the week for any given date. This formula accounts for leap years and varying month lengths.Additionally, it calculates the week number using the ISO 8601 standard, which defines weeks as starting on Monday and the first week containing at least four days in the new year. The calculator also computes the difference in days between the selected date and today’s date.
h = \left(q + \left\lfloor\frac{13(m+1)}{5}\right\rfloor + K + \left\lfloor\frac{K}{4}\right\rfloor + \left\lfloor\frac{J}{4}\right\rfloor – 2J\right) \mod 7
h = day of the week (0=Saturday, 1=Sunday, …, 6=Friday)
q = day of the month
m = month (3=March, 4=April, …, 12=December; January and February are treated as months 13 and 14 of the previous year)
K = year of the century (year \mod 100)
J = zero-based century (\left\lfloor\frac{\text{year}}{100}\right\rfloor)
q = day of the month
m = month (3=March, 4=April, …, 12=December; January and February are treated as months 13 and 14 of the previous year)
K = year of the century (year \mod 100)
J = zero-based century (\left\lfloor\frac{\text{year}}{100}\right\rfloor)
Parameters
Day of the Week
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Week Number of the Year
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Days Until That Date
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Results are for informational purposes only and do not constitute professional advice.