From Excel to Open Office Calc
- Open your file in Excel or Open Office Calc
- File -> Save As
- In the "File Format" menu, select "CSV (Windows) (separator: semicolon) (.csv)"
From Google Sheets
- Open your file in Google Sheets
- File -> Download As
- Select "Comma-separated values (.csv, current sheet)"
- If you have more than one sheet, repeat the same operation.