A date such as 06/07/2026 is ambiguous without knowing the source convention. It might mean 6 July or June 7. Changing the way Excel displays a date afterwards cannot tell you which interpretation the sender intended.

Ask for the source format or check the exporting system’s specification. Keep the untouched file and identify at least one record with a known date. This workflow uses Power Query in desktop Excel for Windows; available import menus depend on the installed edition.

Interpret the original text deliberately

Open the data in the query editor before loading it into the workbook. If an automatic conversion has already interpreted the date column incorrectly, return to the step containing its original text and replace the inappropriate conversion.

Right-click the date column, choose Change Type, Using Locale, then select Date and the locale matching the source convention. Microsoft’s example uses English (United Kingdom) for day/month/year input. Choose based on the data, not simply the language you prefer for the interface.

Power Query’s normal locale can come from the operating system. An explicit conversion is useful when a recurring import comes from a differently configured system.

Test a date that could be silently reversed

Inspect both an unambiguous record, such as a day above 12, and one where day and month are both 12 or below. A column with no errors can still contain reversed dates.

Microsoft suggests extracting day, month and year into temporary columns to verify the interpreted values. Compare those parts with your known source records, then remove the temporary check columns if they are not needed in the finished output.

Keep a note of the chosen source convention with the query. On the next import, check that the supplier has not changed it. Only after the dates are correctly interpreted should you choose a display format for the report’s readers.

References: Microsoft Learn: Power Query data types and locale.