SAMEPERIODLASTYEAR

The SAMEPERIODLASTYEAR function is a DAX time intelligence function used to compare values for the same period in the previous year. It is commonly used to analyze trends and year-over-year (YoY) performance.

This function works only with a Date Table that is marked as a Date Table in Power BI.

Syntax

SAMEPERIODLASTYEAR(<dates>)

• dates – A column from your Date Table containing the dates to shift back one year.

Example 1 – Basic Year-over-Year Sales

Sales LY = CALCULATE(
    SUM(Sales[Amount]),
    SAMEPERIODLASTYEAR(DateTable[Date])
)

• This measure calculates total sales for the same period in the previous year.
• If you filter the report to March 2024, the measure will return total sales for March 2023.

Example 2 – Comparing YTD with Previous Year

Sales YTD LY = CALCULATE(
    TOTALYTD(SUM(Sales[Amount]), DateTable[Date]),
    SAMEPERIODLASTYEAR(DateTable[Date])
)

• This measure calculates Year-to-Date sales for the previous year.
• Useful for comparing cumulative performance over time.

How It Works

• SAMEPERIODLASTYEAR shifts the filter context back by one year.
• It respects the existing filters in visuals or slicers.
• Works with measures rather than calculated columns because it depends on filter context.

Best Practices

• Always use a dedicated Date Table with continuous dates.
• Mark the Date Table as a Date Table to enable correct time intelligence calculations.
• Combine SAMEPERIODLASTYEAR with CALCULATE to perform meaningful aggregations.
• Use in combination with visuals like line charts to highlight year-over-year trends.

Conclusion

SAMEPERIODLASTYEAR is an essential DAX function for year-over-year analysis in Power BI. It allows you to compare performance dynamically across periods, helping to identify trends and monitor business growth over time.