SAMEPERIODLASTYEAR Returns a table that contains a column of dates shifted one year back in time from the dates in the specified dates column, in the current context.
Syntax
SAMEPERIODLASTYEAR(dates)
Parameters
Dates – A column containing dates.
Return Value
A single-column table of date values.
Reference Data
https://docs.microsoft.com/en-us/dax/dax-function-reference