I have an Excel with a number of date fields and text fields.

When I drag and drop Excel spreadsheets to instantly import into FileMaker Pro, the date field in Excel becomes text field in FileMaker. When I changed it to date field, all the dates become 'garbage'

I have to save my Excel into .csv first before doing the import. Is this the only way ?

If the date is still recognizable as such after you import, with the only problem being that FileMaker thinks it is text, then it might help if you use Replace Field Contents to replace the field with the calculation GetAsDate ( [fieldname] ) before converting the field type to Date.

If you do a manual import into an existing file, rather than drag and drop, you could set the above GetAsDate function as an auto-enter calculation for the date field, and check the "Perform auto-enter options" box on import.

Edit: Also, you might want to check the date formatting in the Excel file, because when I dragged and dropped a sample Excel file onto FileMaker, the field with dates entered into it shows up as a Date field in Manage Database, no conversion necessary.