Xiaomi
Create a New Event in the Calendar App auf Xiaomi
The Calendar app on Xiaomi phones bundles several entry types in one Add button: Goal, Reminder, Task and Event. Picking the wrong one is the main reason dates go missing, since only the Event type carries a start and end time, guest list and location field.
To add a real event, open Tap on Calendar ➔ Tap on Add ➔ Choose Goal, Reminder, Task or Event and select Event from that list. Add a title so the entry is recognizable later, then confirm with Add a Title.
The next screen covers everything beyond the basics. Use Set more options to add guests, choose a location, set a repeat interval, and adjust the exact start and end time. This is also where you pick a category, for example Anniversary, so related events stay grouped and easier to filter later.
Once every detail is set, finish with Tap on Save. The event now appears in the calendar grid and triggers any reminder you configured.
If you only need a quick note without a fixed time slot, a Task or Reminder is faster. Choose Event whenever guests, a location or an exact time matter, since those fields only exist in that category.