Can you give us some more background on the issue? Generally, YTD and MTD are found in the 'Calendar' portions of your data model. And to accomplish that, I have something like this.
LET vToday = today();
Calendar:
Load
...
InWeek(TempDate, '$(vToday)', 0) * -1 AS CalCurrentWeek,
InMonth(TempDate, '$(vToday)', 0) * -1 AS CalCurrentMonth,
InYear(TempDate, '$(vToday)', 0) * -1 AS CalCurrentYear,
YeartoDate(TempDate)*-1 as CurYTDFlag,
....
