PL-300 Prepare the data Practice Question
You are a data analyst at an online retailer. You import a CSV file containing product reviews into Power BI Desktop. The file has a column named ReviewDate that currently loads as the Text data type, with values formatted like '2024-07-15T09:30:00Z'. You need to change this column to the Date/Time/Timezone data type, but when you select that type in Power Query, the transformation fails for many rows. You need to resolve the failure while preserving the original timestamp data. What should you do?
⚠ Common exam trap
The trap here is assuming that any ISO 8601 timestamp string will convert directly to Date/Time/Timezone, when Power Query actually requires a numeric UTC offset rather than a trailing Z.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Replace the trailing 'Z' with '+00:00' in the column, then change the data type to Date/Time/Timezone.
The Date/Time/Timezone type in Power Query requires an explicit numeric offset such as +00:00, not the ISO 8601 Z shorthand. Replacing Z with +00:00 preserves the UTC instant and lets the conversion succeed. The other approaches either misinterpret the format, discard required time data, or produce a timezone-less result.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Add a custom column that uses DateTime.FromText on the original values and then delete the original column.
Why it's wrong here
DateTime.FromText returns a datetime value without timezone information, so it cannot produce a Date/Time/Timezone result. Using it would silently drop the offset, which defeats the purpose of converting to Date/Time/Timezone. The original Z suffix would also still cause the same parsing failure.
- ✓
Replace the trailing 'Z' with '+00:00' in the column, then change the data type to Date/Time/Timezone.
Why this is correct
Power Query's Date/Time/Timezone type expects an offset such as +00:00 rather than a Z suffix. Replacing Z with +00:00 preserves the UTC offset and allows the type conversion to succeed. This keeps the original instant intact while satisfying the parser's expected format.
- ✗
Change the column to the Date data type instead, which discards the time and timezone portions and avoids the error.
Why it's wrong here
Switching to the Date type does avoid the conversion error, but it also permanently drops the time and timezone information that the scenario requires you to preserve. The goal is to load the column as Date/Time/Timezone, so discarding the time component does not meet the requirement.
- ✗
Use the Locale option in the Change Type dialog and select English (United States) before applying the Date/Time/Timezone type.
Why it's wrong here
Changing the locale affects how ambiguous date strings are interpreted, but the values already use an unambiguous ISO 8601 format with a Z suffix. The failure is not caused by locale ambiguity; it is caused by the trailing Z indicating UTC. Selecting a locale will not resolve the conversion error for these values.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Microsoft exam blueprint
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