Date.DayOfWeek

Date

Returns the day of the week for a given date.

Syntax

Date.DayOfWeek(dateTime as any, optional firstDayOfWeek as nullable number) as nullable number

Parameters

Name	Type	Required	Description
`dateTime`	`any`	Yes	The date, datetime, or datetimezone value to find the day of the week for.
`firstDayOfWeek`	`number`	No	A Day.Type value indicating the first day of the week. Defaults to Day.Sunday (0). Use Day.Monday (1) for ISO weeks.

Return Value

number — A number from 0 to 6 representing the day of the week.

Remarks

Date.DayOfWeek returns a number from 0 to 6 indicating the day of the week for the given date. By default, 0 represents Sunday and 6 represents Saturday. You can change which day is considered the first day of the week by passing a Day.Type value (e.g., Day.Monday) as the second argument, which shifts the numbering so that the specified day becomes 0. If the input is null, the function returns null.

Examples

Example 1: Find the day of week for each OrderDate

Table.AddColumn(
    Table.SelectColumns(
        Table.FirstN(Sales, 5),
        {"OrderID", "OrderDate"}
    ),
    "DayOfWeek", each Date.DayOfWeek([OrderDate], Day.Sunday), Int64.Type
)

Result

	OrderID	OrderDate	DayOfWeek
1	1	1/15/2024	1
2	2	1/18/2024	4
3	3	2/1/2024	4
4	4	2/10/2024	6
5	5	3/5/2024	2

Example 2: Use Monday as the first day of the week

Table.AddColumn(
    Table.SelectColumns(
        Table.FirstN(Sales, 4),
        {"OrderID", "OrderDate"}
    ),
    "DayOfWeekMon", each Date.DayOfWeek([OrderDate], Day.Monday), Int64.Type
)