Date entry in box format issue

[PeroPuri]

It seems to work now but it gives me back this error when I try to write it in excel

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Program Files (x86)\Python38-32\lib\tkinter\__init__.py", line 1883, in __call__
    return self.func(*args)
  File "C:/Users/pc/Desktop/file/project.py", line 196, in insert
    sheet.cell(row=current_row + 1, column=8).value = self.bday_entry.get()
  File "C:\Program Files (x86)\Python38-32\lib\site-packages\openpyxl\cell\cell.py", line 216, in value
    self._bind_value(value)
  File "C:\Program Files (x86)\Python38-32\lib\site-packages\openpyxl\cell\cell.py", line 199, in _bind_value
    raise ValueError("Cannot convert {0!r} to Excel".format(value))
ValueError: Cannot convert {'day': 11, 'month': 11, 'year': 1999} to Excel

I've tried datetime.strptime to convert the date but with no luck.