The modern date control within a form does not display the value of an item's date column in FormMode.Edit.
FormMode.View:
When clicking "Edit" in SharePoint, turning FormMode to FormMode.Edit with SharePointIntegration > OnEdit = EditForm(Form):
The value disappears... and the SubmitForm validation fails, asking me to enter a date for this column. Value(), Text() and DateValue() functions inside of the date picker's DefaultDate property are not helpful. I have switched DateTimeZone values to .Local and .UTC to no avail. I even added a variable to LookUp() the item's Date Of Complaint, then set the date picker's value to that. NOTHING! Does anyone have a fix for this? I have not seen any posts about it.
Edit 4/28/26:
Thank you all for the quick responses. The solution is to remove and re-add the date picker control and withhold the update to the date picker (for now). I will not be switching back to the classic control, because that UI is absolutely disgusting and not the answer I was looking for -- nor does it fit the fluent design of all other modern controls.