Date.StartOfMonth

Date

Returns the first day of the month for a given date.

Syntax

Date.StartOfMonth(dateTime as any) as any

Parameters

Name	Type	Required	Description
`dateTime`	`any`	Yes	The date, datetime, or datetimezone value to find the start of the month for.

Return Value

any — The first day of the month containing the input date.

Remarks

Date.StartOfMonth returns the first day of the month for the given date, datetime, or datetimezone value. The return type matches the input type. If the input is null, the function returns null.

Examples

Example 1: Find the start of each order's month

Table.AddColumn(
    Table.SelectColumns(
        Table.FirstN(Sales, 5),
        {"OrderID", "OrderDate"}
    ),
    "MonthStart", each Date.StartOfMonth([OrderDate]), type date
)

Result

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

Example 2: Start of month from a scalar value

#table(
    type table [Date = date, StartOfMonth = date],
    {{#date(2024, 4, 15), Date.StartOfMonth(#date(2024, 4, 15))}}
)