Date.StartOfYear Function in Power Query

The Date.StartOfYear function in Power Query (M language) returns the first day of the year for a given date, datetime, or datetimezone value, with the time component set to midnight (00:00:00).

Syntax

Date.StartOfYear(
    dateTime as any
) as any

The function has the following parameter:

• dateTime: A value of type date, datetime, or datetimezone for which you want the start of the year.

Return Value:

• Returns a value of the same type (date, datetime, or datetimezone) representing January 1st of that year.
• Preserves the time zone if the input is datetimezone.

Example: With a datetime.

Power Query M

let
    Source = Date.StartOfYear(#datetime(2025, 8, 24, 15, 30, 45))
in
    Source        

The output of the above code is:
#datetime(2025, 1, 1, 0, 0, 0)

Example: With a date.

Power Query M

let
    Source = Date.StartOfYear(#date(2025, 5, 10))
in
    Source   

The output of the above code is:
#date(2025, 1, 1)

Example: With datetimezone.

Power Query M

let
    Source = Date.StartOfYear(#datetimezone(2025, 8, 24, 10, 0, 0, 05, 30))
in
    Source   

The output of the above code is:
#datetimezone(2025, 1, 1, 0, 0, 0, 5, 30)