OnePlus
Show or Hide Birthday Reminders in Calendar auf OnePlus
Birthday reminders in the OnePlus Calendar app are pulled from your synced contacts, not added as manual events. Each Google Account linked to your phone has its own birthday visibility setting, which explains why one account shows dates while another stays completely silent.
To check or change this behavior, open Calendar app ➔ Open the menu ➔ Open the Settings ➔ Tap on Birthdays ➔ Enable or disable Contacts. This toggle exists separately for every account, so repeat the process for each Google Account you use on the device.
Switching the toggle off removes birthday entries from the calendar view right away, but it does not delete the birthday stored in the contact itself. If reminders are missing entirely rather than just hidden, check that contact sync is active for that account, since disabled sync stops birthdays from reaching the calendar at all.
If you only want to mute reminders for a single person instead of a whole account, this setting will not help, since it works per account and not per contact. In that case, removing the birthday from the individual contact entry is the more targeted fix.