Excel deleting data

Hi Louis,

Excel normally does not delete older dates by itself, so based on your sharing, we need to determine whether the values are truly being erased, hidden, or replaced through syncing/refresh activity.

1/ Try recovering the missing dates first if possible

If the workbook is stored in OneDrive or SharePoint

• Open the workbook and click the file name at the top of the Excel window.
• Select Version History > check if there is any available version from around the time when the missing dates were still present
• Copy the dates into a new recovery workbook

If the workbook is stored locally on your Mac only

• Check whether macOS Time Machine has an earlier copy.
• You can also look for AutoRecovery files to see if it helps: go to Finder > Go > Go to Folder > enter this path ~/Library/Containers/com.microsoft.Excel/Data/Library/Application Support/Microsoft

2/ Check whether the data is deleted or only invisible

Choose a cell where a date should appear and look at the formula bar.

• If the date appears in the formula bar, the data is still there, but formatting is hiding it. You can try clearing formatting by selecting the entire affected date column > Home > Clear > Clear Formats and set Number Format to Date.
• If the formula bar is blank, the value has actually been removed or replaced. In this case, may I ask whether your Excel workbook imports information from another file, database, CSV, CRM system, Power Query, or connected service? If that's the case, the data entries could be overwritten during query/connection refresh.

Please give it a try and let me know what the outcome is. Should you have any further questions or need additional assistance, please feel free to share them in the comment below. I'm very happy to help.

Thank you again for your cooperation and understanding. Hope to hear from you soon.

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