bug: obj.astimezone() raised OSError: [Errno 22] Invalid argument

[Creeper19472]

Duplicate Check

• I have searched the opened issues and there are no duplicates

Describe the bug

Flet encountered this error when handling a dialog containing a DateRangePicker.

Code sample

Code

import flet as ft


def main(page: ft.Page):
    range_picker = ft.DateRangePicker()
    page.add(range_picker)
    page.show_dialog(range_picker)


if __name__ == "__main__":
    ft.run(main)

To reproduce

1. Run the repro code
2. It fails

Expected behavior

No exceptions thrown

Screenshots / Videos

Captures

Operating System

Windows

Operating system details

Windows 11 25H2 (26200.7171)

Flet version

0.70.0.dev6999

Regression

I'm not sure / I don't know

Suggestions

No response

Logs

Logs

Unhandled error in main() handler
Traceback (most recent call last):
  File "d:\[REDACTED]\.venv\Lib\site-packages\flet\app.py", line 269, in on_session_created
    main(session.page)
    ~~~~^^^^^^^^^^^^^^
  File "d:\[REDACTED]\src\include\ui\issues\daterange.py", line 6, in main
    page.add(range_picker)
    ~~~~~~~~^^^^^^^^^^^^^^
  File "d:\[REDACTED]\.venv\Lib\site-packages\flet\controls\base_page.py", line 284, in add
    self.update()
    ~~~~~~~~~~~^^
  File "d:\[REDACTED]\.venv\Lib\site-packages\flet\controls\page.py", line 448, in update
    self.__update(self)
    ~~~~~~~~~~~~~^^^^^^
  File "d:\[REDACTED]\.venv\Lib\site-packages\flet\controls\page.py", line 457, in __update
    self.session.patch_control(c)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~^^^
  File "d:\[REDACTED]\.venv\Lib\site-packages\flet\messaging\session.py", line 138, in patch_control
    self.__send_message(
    ~~~~~~~~~~~~~~~~~~~^
        ClientMessage(
        ^^^^^^^^^^^^^^
    ...<2 lines>...
        )
        ^
    )
    ^
  File "d:\[REDACTED]\.venv\Lib\site-packages\flet\messaging\session.py", line 281, in __send_message
    self.__conn.send_message(message)
    ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "d:\[REDACTED]\.venv\Lib\site-packages\flet\messaging\flet_socket_server.py", line 221, in send_message
    m = msgpack.packb(
        [message.action, message.body],
        default=configure_encode_object_for_msgpack(BaseControl),
    )
  File "d:\[REDACTED]\.venv\Lib\site-packages\msgpack\__init__.py", line 36, in packb
    return Packer(**kwargs).pack(o)
           ~~~~~~~~~~~~~~~~~~~~~^^^
  File "msgpack/_packer.pyx", line 279, in msgpack._cmsgpack.Packer.pack
  File "msgpack/_packer.pyx", line 276, in msgpack._cmsgpack.Packer.pack
  File "msgpack/_packer.pyx", line 265, in msgpack._cmsgpack.Packer._pack
  File "msgpack/_packer.pyx", line 232, in msgpack._cmsgpack.Packer._pack_inner
  File "msgpack/_packer.pyx", line 270, in msgpack._cmsgpack.Packer._pack
  File "msgpack/_packer.pyx", line 213, in msgpack._cmsgpack.Packer._pack_inner
  File "msgpack/_packer.pyx", line 265, in msgpack._cmsgpack.Packer._pack
  File "msgpack/_packer.pyx", line 232, in msgpack._cmsgpack.Packer._pack_inner
  File "msgpack/_packer.pyx", line 265, in msgpack._cmsgpack.Packer._pack
  File "msgpack/_packer.pyx", line 232, in msgpack._cmsgpack.Packer._pack_inner
  File "msgpack/_packer.pyx", line 265, in msgpack._cmsgpack.Packer._pack
  File "msgpack/_packer.pyx", line 232, in msgpack._cmsgpack.Packer._pack_inner
  File "msgpack/_packer.pyx", line 270, in msgpack._cmsgpack.Packer._pack
  File "msgpack/_packer.pyx", line 213, in msgpack._cmsgpack.Packer._pack_inner
  File "msgpack/_packer.pyx", line 267, in msgpack._cmsgpack.Packer._pack
  File "d:\[REDACTED]\.venv\Lib\site-packages\flet\messaging\protocol.py", line 77, in encode_object_for_msgpack
    obj = obj.astimezone()
OSError: [Errno 22] Invalid argument

Additional details

No response

[Creeper19472]

This issue appears to be caused by the default value of first_date (1900-01-01).

[ndonkoHenri]

Hum, it works normally on my end (macOS 15, 0.70.0.dev6999):

Can you please create a new venv and retry? (btw, no need to add the picker to the page - show_dialog is sufficient)

[Creeper19472]

@ndonkoHenri Doesn't work. I'm using uv and Python 3.14 for the new venv. It's worth mentioning that I'm located in Asia.

[ndonkoHenri]

Ah, seems to be a known Python Windows-specific issue.

Will have a closer look.