Issue with SAMEPERIODLASTYEAR in Enhanced DAX Time Intelligence (Preview) Week 53 returns incorrect

Hi bpratyusha,

Let me clarify this issue for you...this issue occurs because SAMEPERIODLASTYEAR uses a standard 365 day calendar while your fiscal calendar has 364-368 days and sometimes 53 weeks

So here is some Approaches to solve it you can try:

• Use Custom DAX with FILTER
  • Replace your LY sales measure with this pattern:

LY Sales Corrected = 
VAR CurrentFiscalYear = SELECTEDVALUE('Date(454)'[fiscal_year])
VAR CurrentFiscalDay = SELECTEDVALUE('Date(454)'[fiscal_day_in_year])
VAR PreviousFiscalYear = CurrentFiscalYear - 1
RETURN
CALCULATE(
    SUM('fact'[sales]),
    FILTER(
        ALL('Date(454)'),
        'Date(454)'[fiscal_year] = PreviousFiscalYear &&
        'Date(454)'[fiscal_day_in_year] = CurrentFiscalDay
    )
)

• Handle Week 53 Specifically

LY Sales Week53 Fixed = 
VAR CurrentDate = MAX('Date(454)'[calendar_date])
VAR CurrentFiscalYear = MAX('Date(454)'[fiscal_year])
VAR CurrentFiscalWeek = MAX('Date(454)'[fiscal_week_in_year])
VAR LYDate = SAMEPERIODLASTYEAR('Date(454)'[calendar_date])

RETURN
IF(
    CurrentFiscalWeek = 53 &&
    NOT EXISTS(
        FILTER(
            ALL('Date(454)'),
            'Date(454)'[fiscal_year] = CurrentFiscalYear - 1 &&
            'Date(454)'[fiscal_week_in_year] = 53
        )
    ),
    BLANK(),
    CALCULATE(SUM('fact'[sales]), LYDate)
)​

• Date Table Enhancement

  • Add a column to your date table to identify valid same-period-last-year dates:

// Add this as a calculated column to DimDate
Valid SPY Date = 
VAR CurrentFiscalYear = [fiscal_year]
VAR CurrentFiscalDay = [fiscal_day_in_year]
RETURN
CALCULATE(
    COUNTROWS('Date(454)'),
    FILTER(
        ALL('Date(454)'),
        'Date(454)'[fiscal_year] = CurrentFiscalYear - 1 &&
        'Date(454)'[fiscal_day_in_year] = CurrentFiscalDay
    )
) > 0

I suggest starting with First Solution as it's the most reliable for custom fiscal calendars. It directly matches fiscal days between years rather than relying on calendar date offsets.