To open a CSV file in Excel so that you don’t lose the TEXT formatting:
  1. Open Excel
  2. Click New, then click on Blank workbook
  3. Click on the Data tab
  4. Click Get External Data From Text
  5. Navigate to the CSV-formatted file saved on your system, select it, then click Import (When browsing to find the file, set browser to look for All Files or for Text Files)
  6. This will open the Text Import Wizard
  7. In Import Step 1 of 3 – Click on Delimited, then click Next
  8. In Import Step 2 of 3 – Check the Comma box, then click Next
  9. In Import Step 3 of 3 – Select Text
  10. Click Finish, then OK
 
To stop auto-formatting numbers to dates in Excel when editing a .CSV file :
  1. Select the cells that numbers will  be entered in
  2. Press Ctrl + 1 (the 1 in the row of numbers above the QWERTY keys) to open Format Cells.
  3. Select Text, and then click OK.

If you only have a few numbers to enter, you can stop Excel from changing them into dates by entering:
  1. A space before you enter a number. The space remains in the cell after you press Enter. (See Notes)
  2. An apostrophe (‘) before you enter a number, such as ’11-53 or ‘1/47. The apostrophe isn’t displayed in the cell after you press Enter. (Recommended)