Rules / Formatting

Provide format string for "Date" columns

info DATECOLUMN_FORMATSTRING · ported · scope: Column, CalculatedColumn, CalculatedTableColumn

What it checks

DateTime columns with date in the name whose format string is not exactly mm/dd/yyyy.

Why it matters

A date column with no format string is shown however the viewer's locale and the visual decide, so the same column can read 3/4/2026 in one visual and 4 March 2026 in another. A format string on the column fixes the presentation once for every report. The source ruleset picked the US short date as its convention.

How to fix it

In Power BI Desktop, select the column and set the Format under Column tools. In the TMDL file, add formatString: mm/dd/yyyy under the column. The expected format is US-centric; if your convention differs, set the format you want and turn this rule off in pbiplint.config.json, because only the exact string passes.

Quirks

• The name test is a substring, so any column containing the letters date, such as Update Time, is matched.
• Any other format fires, including dd/mm/yyyy and yyyy-mm-dd.

Links

• https://github.com/microsoft/Analysis-Services/blob/master/BestPracticeRules/BPARules.json

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