Hi @Erno_Ervasti1 - no need to change to a date format in Make!
In your Google Sheet: select the entire column (C), and then in the menu, select Format > Number > (choose a date format from the list).
I don’t know what the menu looks like in Finnish but here’s a help article from Google with a video: Format numbers in a spreadsheet - Computer - Google Docs Editors Help
Cheers!