PARALLELPERIOD() in Power BI DAX

Here’s a short description and example of PARALLELPERIOD() in Power BI DAX:

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🔁 What it does:

PARALLELPERIOD() shifts the dates in the current context by a specified number of intervals (month, quarter, or year) — but keeps the same length of period.

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🧮 Syntax:

PARALLELPERIOD(<dates>, <number of intervals>, <interval type>)

• <dates> → a date column (e.g., 'DateTable'[Date])
• <number of intervals> → -1 for previous, 1 for next
• <interval type> → "month", "quarter", "year"

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🧮 Example: Previous Year Sales

Sales PY = 
CALCULATE(
    SUM(Sales[Sales]),
    PARALLELPERIOD('DateTable'[Date], -1, YEAR)
)

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📊 How it works:

Year	Month	Sales	Sales PY (ParallelPeriod -1 Year)
2025	Jan	24,000	22,000 (from Jan 2024)
2025	Feb	15,800	13,000 (from Feb 2024)

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✅ Tip: Unlike SAMEPERIODLASTYEAR(), PARALLELPERIOD() doesn’t preserve day granularity — it just shifts the whole month/quarter/year.