I haven't noticed any issues, but I downloaded Google's stock calendar app and disabled the LG one.
What does the Google one bring that's better?
I've discovered why the calendar was jumping forward by a day. It seems to be all about the time you try and enter something. If you do it at, say, 7.40am, the reminder automatically rounds up to the next hour, so will say 8.00am. I then tick 'all day' as I only use the calendar to put day to day stuff in, and delete as I go along. If, however, you try the same thing at 11.15pm (as I was last night), it then jumps to 12am, so the calendar then adjust the date to the next day. If you then tick 'all day', it remains on the next day until it's changed manually.
Glad I spotted what was going on, but seems a bit of a unnecessary function, particularly if you're putting am important reminder in well in advance, and you then see it the day after you've supposed to have done it.