Dax Function: STARTOFYEAR
Category: Time Intelligence Functions
The STARTOFYEAR function in Power BI is a DAX time intelligence function that returns the first date of the year in the context of the given date column. It helps anchor time-based calculations by providing the starting point for annual data analysis and comparison.
Purpose of the Function
The STARTOFYEAR function is used to extract the first date of the current year, given a date column. It simplifies yearly aggregations, cumulative calculations, and time-based comparisons in a report or analysis.
Type of Calculations
- Annual Aggregation: Aggregating data from the beginning of the year (e.g., sum or average from January 1st to the current date).
- Time Period Calculations: Comparing data from the start of the year to another time period (e.g., comparing Q1 of the current year with Q1 of the previous year).
- Trend Analysis: Identifying trends that start from the first day of the year.
Practical Use Cases
- Year-to-Date Calculations: Compute cumulative totals or averages from the start of the year.
- Year-over-Year Comparison: Compare data between two specific years starting from January 1st.
- Annual Forecasting: Use the first date of the year to project future performance based on historical trends.
STARTOFYEAR(<dates>)
| Parameter | Type | Description |
|---|---|---|
dates | Column | A column containing date values, typically from a well-structured date table. |
How Does STARTOFYEAR Dax Function Works
- Filter Context Evaluation: The function evaluates the provided date column (
dates) based on the active filters. - Year Identification: It identifies the year for the given context. For example, if the context is set to a date in 2025, it returns the first date of 2025 (i.e., January 1, 2025).
- First Date Extraction: The first date of the identified year is returned as a single-row table.
For example, if the context is any date in 2025, the function will return January 1, 2025.
What Does It Return?
The STARTOFYEAR function returns a single-column table containing the first date of the year in the specified filter context.
When Should We Use It?
- Cumulative Calculations: When performing year-to-date (YTD) calculations or aggregating values from January 1st of the current year.
- Yearly Comparisons: Comparing the first date of this year with the first date of last year.
- Annual Performance Tracking: To assess annual performance starting from the first day of the year.
Examples
Basic Usage
First Date of Year = STARTOFYEAR(Dates[Date])
This simply returns the first date of the year, for example, January 1, 2025, if the context is set to that year.
Year-to-Date Revenue:
YTD Revenue =
CALCULATE(
SUM(Sales[Revenue]),
Dates[Date] >= STARTOFYEAR(Dates[Date])
)
This calculates the total revenue from the first day of the year to the current date.
Advanced Usage
YoY Revenue Growth =
DIVIDE(
CALCULATE(SUM(Sales[Revenue]), STARTOFYEAR(Dates[Date])),
CALCULATE(SUM(Sales[Revenue]), SAMEPERIODLASTYEAR(STARTOFYEAR(Dates[Date])))
) - 1
This formula calculates the year-over-year growth in revenue from the first day of the current year to the first day of the previous year.
Tips and Tricks
- Use with CALCULATE: When combined with
CALCULATE,STARTOFYEARhelps in aggregating data over the span of the year. - Use with Other Time Functions: Combine with other time intelligence functions like
SAMEPERIODLASTYEAR,TOTALYTD, orYEARto build more complex calculations. - Avoid Redundant Use: Don’t apply
STARTOFYEARmultiple times in the same expression unless necessary, as it can lead to inefficient calculations.
Potential Pitfalls:
- Make sure the date column (
dates) is well defined and continuous to avoid errors or inaccuracies.
Performance Impact of STARTOFYEAR DAX Function:
- Efficient Use of Date Tables: Make sure your date table is indexed, as this improves the performance of time intelligence functions like
STARTOFYEAR. - Large Datasets: Filter out unnecessary data to optimize performance when applying this function to large datasets.
Related Functions You Might Need
ENDOFYEAR: Returns the last date of the current year.TOTALYTD: Computes year-to-date totals for a given measure.DATESYTD: Returns all dates from the start of the year to the current context.FIRSTDATE: Returns the first date in the current context, not limited to the year.
Want to Learn More?
For more information, check out the official Microsoft documentation for STARTOFYEAR. You can also experiment with this function in your Power BI reports to explore its capabilities.
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It returns the first date of the current year based on a given date column.
No, the function works with calendar years. For fiscal year support, modify your date table.
It returns a single-row table with the first date of the year.
STARTOFYEAR returns the first date of the year, while STARTOFQUARTER returns the first date of a specific quarter.
Yes, you can use it in combination with CALCULATE to compute year-to-date metrics.
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