I think I remember Glide saying that for now dates need to be entered in MM/DD/YYYY format. YYYY/MM/DD and ISO should work too. In they future I think they will try to get the region settings from the sheet.
Does the date show correctly on a phone? The calendar uses the device’s regional local settings for displaying the date. The same app will show the differently in the US compared to Europe. What region is your browser set to?
I would set the date in US, Y/M/D, or ISO in the sheet, then adjust the formatting of the date in the data tab.