Date of Birth not saving

I have the same problem.
Before 1970.01.02 I am not able to set birthday.

The Same here. I wasn't able to save my date of birth. Set date works without any problem, but after leaving the date-setting the date wasn't shown and on reentering the date-setting i saw May 2002 as date again.

For now I've entered 1-1-1970, the "oldest" the app allows. So using this app can be rejunevating. And it's sortof an honour to be born at Unix time 0. Always wanted this t-shirt with a positive number on it: https://geeksta.net/tools/born-at-unix-time/
Joking aside, I hope it will be fixed soon!

The Garmin Support Centre have acknowledged that the issue we've all experienced did exists and have passed it onto their Software Engineers. How long a resolution will take I haven't been told though I suppose that's to be expected, however it's good to know they agree there is a problem.

If I hear anything I'll let you know though I suppose we may only see a fix once there's an update to the apps and website.

This is happening to me too! My VO2 max went from superior to poor because the app thinks i’m 16 instead of 65!! Also Intensity minutes are not saving for Mondays.

I added a Forerunner 935 to my Connect account and set all user settings for it; DOB 1-1-1970. There was already an Epix in use that had my correct birth year (< 1970). After syncing, the user settings on the Forerunner listed birth year 2113.

Just to say that in my case (edge 820 and F5) it took me a while, but then I realised that setting the age needs to be done on GC web, for each device, in the settings page reached from "devices and sync status", under the user settings tab. The phone GC app will not take changes, and something gets messed up if they don't match.
My suggestion would be to have birth date under the user account, instead of under the devices, because the logical assumption is that a user's age does not change whether he/she has one or several devices.
Anyway, once I had made sure both the edge, and the F5 device/user settings had my correct birthdate, there was no issue anymore, I've synced several times since, and it's all stable.

My date of birth now accepted. Had to go to online and enter birthday again, but once I did that it accepted that I was 61 and not 16!

I can enter a b'date < 1-1-1970 in the user settings under Device Settings, but not in the overall user settings in the user profile. That takes only dates later than 1-1-1970, and that date then overrides the date under the Device Settings, which is synced to the devices and messes up every calculation that uses the DOB. Currently have to enter DOB in all the devices' settings and leave the overall-userprofile-DOB alone, then the devices will work correctly.
Edit: never mind, apparently the order in which you change things in the mobile app and/or the web inteface affects the net results after syncing. No idea what the logic is.