I can’t sign in from the first startup birthday selection and then the sign-in screen.
I tried restarting, reinstalling, Google account, Apple account, everything.
Birthdays are entered accurately. (Japanese calendar input because I live in Japan)
It is also set up correctly on the account for sign-in. (In the account, it is set in the Western calendar)
iPhone15Pro（17.6.1）
I contacted support, but I was confused by the story of the Android browser.
If you know anything, it would be helpful if you could tell me. Thank you in advance.
Through interaction with support, I was able to resolve my own.
The Japan version seems to have a bug at the moment.
If you have set the calendar system display to Japanese in your iPhone settings, you will be asked to enter the Japanese calendar when you sign in.
However, due to a bug, this does not seem to allow you to sign in correctly.
In that case, you will be able to enter it correctly by setting the calendar system to Western in the iPhone settings. (Setting the calendar system, not the language setting)
If there is anyone in Japan who has a similar problem, please try it.