Hi ​@Zsófia Pálffi 

Thanks for reporting this! To better understand what's happening, could you please share a few more details?

• Are you copy-pasting data from Excel, or using the Upload option?

• When you say you “change the type of the column to start date,” are you referring to a table widget or a timeline in Miro?

• What is the exact date format in your Excel file (e.g. DD/MM/YYYY, MM/DD/YYYY, 2024-06-01)?

• What’s the exact error message or notification you receive?

• Does this happen with all date columns or just certain rows?

 If possible, could you also upload a screenshot or short screen recording showing the issue?

That will help us investigate or pass this along to the support team more efficiently if needed.