I have same issue with calendar where it shows correct time(CST) in left column on my calendar but has PST inside details (blocked area).
Initially I thought it was apple forcing me to see what the time was in California (PST) but seeing other people with the same issue in different time zones showing a different time zone than PST as secondary time, that is not the case. What is most irritating is if I want to change the time, it comes up in PST on the selection wheel which really throws me off.
I found an interesting thing. If I closed my calendar, change the time zone on and then back off (even though I had it as CST anyway). I then opened my calendar and created a new event. Voila, no secondary timezone shown. It did not fix the calendar entries I already had but if I deleted an existing one and re-added it, it is not showing PST time.
I'm not going to try deleting my exchange account to see if this solves the issue but maybe someone else wants to take a shot at it.
Please remember, this only worked if the calendar was shutdown when this worked. I tried it when calendar was open and it did not work.
This is what looked like before my flip flop
this is what calendar looked like after flip flop
this is what calendar looked like after flip flop on main screen