On my S24 ULTRA, I added a reminder to my Samsung calendar for an annual reminder on a specific date. The calendar changed the date once Isaved it, closed the calendar, then disappeared when I opened the calendar again!!! 😯😯😯
I don't know why the date changed after you saved it. You might not have quick checked that you put it on the correct year (or month) as the start date. I sometimes catch myself before I save and notice the wrong date was set. The calendar has a search feature. You can search the calendar for it. If it disappeared completely, then it was likely not saved and you can just set it up again.
