To stop Excel from reinterpreting dates in a CSV, import the file through Excel’s data import tools and set the date column’s format before loading it. In Excel for Mac, the From Text (Legacy) wizard offers an explicit Text option to preserve date strings exactly, or a Date option with a chosen order, such as MDY or DMY, when you need working Excel dates.

Why dates change when you open a CSV

A CSV stores values as text fields; it does not retain Excel cell formatting or tell Excel which regional date convention to use. A value such as 03/04/2025 could mean March 4 or April 3. If Excel interprets it automatically, it can change how the value displays or what date it represents. Microsoft notes that a CSV import can require choosing a date format to match the source data. Import or export text (.txt or .csv) files

If the date is an identifier or must remain exactly as written, import it as text. If you need to sort dates chronologically or calculate with them, import as a date and select the order that matches the source. Decide this before loading: changing a cell’s display format afterward cannot reliably restore a value Excel has already misinterpreted.

Import with the Mac Text Import Wizard

  1. Open a workbook in Excel, then choose Data > From Text (Legacy). Select the CSV in the Finder window and choose Open. If From Text (Legacy) is missing, check Excel’s version and Data tab; Microsoft documents this option for Excel for Mac, but available commands can vary across releases. Its Mac instructions list the wizard steps and column-format controls. Import and shape data in Excel for Mac (Power Query)

  2. In the first wizard screen, select Delimited for a typical CSV. Keep the file origin at its default unless you know the file uses a different character encoding. Choose Next.

  3. In the delimiter screen, select Comma and check the preview. Confirm that each field appears in its own column. If commas within a field are enclosed in quotation marks, check that the preview keeps that field together; the text qualifier is usually a double quote. Choose Next.

  4. In the final screen, select the date column in the preview. Under Column data format, choose Text to preserve the original characters, including leading zeros or an ambiguous date string. To create actual dates, choose Date and the correct order—such as MDY, DMY, or YMD—based on the source file. Verify several rows in the preview, especially dates where both the day and month are 12 or lower. Microsoft’s Mac guidance confirms that you can set each column’s format and date format here. Import and shape data in Excel for Mac (Power Query)

  5. Choose Finish, select where to place the imported data, then choose OK. Check the resulting column against the original CSV before using it. If you imported as text, the values should remain text; convert them later only after confirming their format and meaning.

If you use Power Query on Mac

In Excel for Microsoft 365 for Mac, you can also select Data > Get Data, choose Text/CSV, and use Transform Data before loading. Power Query is generally available on Mac to Microsoft 365 subscribers running version 16.69 or later, according to Microsoft. Its preview can detect column types, so inspect the date column rather than assuming the detected type matches your source. Import and shape data in Excel for Mac (Power Query)

Microsoft documents that Power Query can shape data in the editor, but its Mac import guidance does not describe a specific date-order control in the CSV preview. If you need a documented, explicit choice between preserving dates as text and interpreting them in a particular order, use From Text (Legacy) when available. If the command is unavailable in your Excel build, avoid relying on automatic conversion for ambiguous dates; first make a copy of the CSV and change the date strings to an unambiguous format, or use a documented import route that lets you set the column type.

Check the result and protect the original

Compare several imported values with the source, then test dates from both sides of the month/day ambiguity. A date like 21/04/2025 can reveal that a column is day-first; a value like 03/04/2025 alone cannot. For text-preserved values, the cells are labels rather than usable date values. For true dates, set the display format you want after import, but remember that display formatting changes appearance, not the date interpretation already made.

Keep the original CSV unchanged until you have confirmed the imported values. If you discover a wrong interpretation, discard the imported sheet and repeat the import with the correct column setting rather than trying to repair a mixed or misread column by changing its appearance.

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