Day of the Week Calculator

A day of the week calculator converts a calendar date into its weekday name. It is useful when checking historical events, planning future appointments, preparing schedules, or answering questions such as whether a birthday occurred on a Saturday. Enter a valid date and the calculator returns one of the seven weekdays without requiring you to move through a calendar month by month. The calculation follows the proleptic Gregorian calendar. That means modern Gregorian leap-year and month rules are extended backward for earlier years, even before a particular country historically adopted that calendar. A regular year has 365 days, which advances the weekday by one position. A leap year has 366 days and advances it by two. Years divisible by four are normally leap years, century years are not, and century years divisible by four hundred are leap years after all. February therefore has 29 days in 2000 and 2024, but only 28 days in 1900. Computer date arithmetic can be affected by local time zones when a date is interpreted at midnight. This tool avoids that ambiguity by constructing and checking the selected year, month, and day in Coordinated Universal Time. Since a calendar weekday does not depend on the viewer's time zone, the same entered date produces the same answer wherever the calculator runs. It also verifies that the date components survive construction unchanged, preventing impossible dates such as April 31 from rolling silently into the next month. For modern planning, the result can be compared directly with a standard calendar. For historical research, remember that communities changed calendars at different times. A date recorded under the Julian calendar may need conversion before entering it here. The calculator does not infer the calendar used by a source document, religious tradition, or jurisdiction. When accuracy matters, confirm the original calendar convention, convert the date if necessary, and then use this result as a dependable Gregorian weekday reference.