Using Excel AutoFill for dates
When copying dates into our excel sample files the date format may change and you may get this error message as a result “Invalid file format. Certain months have been included multiple times.”
The best way to avoid this is to use the Excel AutoFill – Fill Months feature. Please see the steps below for more information.
1. Start with a sample file.
2. Copy and paste your performance values into the “default” column.
3. Delete all cells in the “Date” column except the first one and adjust it´s value accordingly (inception of your performance).
4. Click the first cell in the “Date” column to make it active. Then click the fill handle (a small square at the bottom right of the highlighted rectangle) and drag down to copy values from the first cell.
5. Click the plus sign at the bottom right of the highlighted selection and click Fill Months. Please note the plus sign may sometiome appear at the top as well.
6. Check the result. There should be a series of consecutive months in the Date column.
7. Save the file and import it.