The answer is that SAMEPERIODLASTYEAR does not handle leap years correctly for February 29. This DAX function shifts the date context by exactly 365 days, so when the current period includes February 29 in a leap year, it attempts to map back to February 28 of the prior year, causing a mismatch and returning blank or incorrect results for that date. On the Microsoft Power BI Data Analyst PL-300 exam, this tests your understanding of time intelligence functions and their limitations with irregular calendar patterns; a common trap is assuming SAMEPERIODLASTYEAR works symmetrically for all dates. Remember, SAMEPERIODLASTYEAR is a 365-day shift, not a one-year calendar shift—so for leap day, it lands on the wrong date. A useful memory tip: “365 days, not one year—February 29 disappears.”
PL-300 Model the data Practice Question
This PL-300 practice question tests your understanding of model the data. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
Refer to the exhibit.
```
DEFINE
MEASURE Sales[Total Sales] = SUM(Sales[Amount])
MEASURE Sales[Sales YoY] =
VAR CurrentSales = [Total Sales]
VAR PreviousSales = CALCULATE([Total Sales], SAMEPERIODLASTYEAR('Date'[Date]))
RETURN
DIVIDE(CurrentSales - PreviousSales, PreviousSales)
```
Refer to the exhibit. A Power BI developer wrote the DAX measure above to calculate year-over-year sales growth. When tested in a matrix visual with Year on rows and Month on columns, the measure returns incorrect results for the month of February in leap years. What is the likely cause?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
SAMEPERIODLASTYEAR does not handle leap years correctly for February 29.
Option B is correct because SAMEPERIODLASTYEAR shifts the date context by exactly 365 days, which can cause issues in leap years for dates after February 28. Option A is incorrect because DIVIDE handles division by zero. Option C is incorrect because the measure is correctly defined as a measure. Option D is incorrect because the variable is fine.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
SAMEPERIODLASTYEAR does not handle leap years correctly for February 29.
Why this is correct
SAMEPERIODLASTYEAR shifts by 365 days, which may map to a different date in leap years.
Related concept
Read the scenario before looking for a memorised answer.
✗
The measure should be a calculated column, not a measure.
Why it's wrong here
Measures are appropriate for dynamic calculations.
✗
The variable CurrentSales is not needed; use SUM directly.
Why it's wrong here
Variables improve readability and performance.
✗
The DIVIDE function returns an error when PreviousSales is zero.
Why it's wrong here
DIVIDE returns BLANK() when denominator is zero.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which PL-300 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Model the data — This question tests Model the data — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: SAMEPERIODLASTYEAR does not handle leap years correctly for February 29. — Option B is correct because SAMEPERIODLASTYEAR shifts the date context by exactly 365 days, which can cause issues in leap years for dates after February 28. Option A is incorrect because DIVIDE handles division by zero. Option C is incorrect because the measure is correctly defined as a measure. Option D is incorrect because the variable is fine.
What should I do if I get this PL-300 question wrong?
Identify which PL-300 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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