Weekday Calculator
Find what day of the week any date falls on — past, present, or future. Enter values for instant results with step-by-step formulas.
Reviewed by Abdullah, Technical Content Specialist
Formula
ISO Week Number = 1 + floor((OrdinalDate - weekday + 10) / 7)
The day of the week is determined by the Date object's internal calendar calculations. The ISO week number is computed by finding the Thursday of the current week (since ISO weeks are defined by their Thursday), then counting the number of weeks from January 4 of that year (which is always in ISO Week 1). The day of year is the count of days elapsed since January 1.
Worked Examples
Example 1: Finding the Day of the Week
Problem:What day of the week is July 4, 2026?
Solution:Enter July 4, 2026 into the calculator.\nThe calculator determines the day using date arithmetic.\nJuly 4, 2026 falls on a Saturday.\nIt is day 185 of the year, in week 27.
Result:Saturday | Day 185 | Week 27 | Q3
Example 2: Year Progress Check
Problem:How far through the year is September 15, 2026?
Solution:September 15 = Day 258 of 365\n258 ÷ 365 = 70.7% through the year\nDays remaining: 365 - 258 = 107\nWeek number: 38, Quarter: Q3
Result:Day 258 of 365 | 107 days remaining | Week 38
References
Reviewed by Abdullah, Technical Content Specialist · Editorial policy