Oooh, calendar freezing, that sounds really bad.
You are the first person i have read a post from who has one of the three problems i had, data not syncing. If i entered the data on iCal, it would sync to iPhone, but nothing i entered on iPhone would sync to iCal (or to iCloud of course).
(one problem, upon updating to OS8 was GMT showing up all over my calendar on the iPhone, another problem was that the Calendar would give me a 30 minute alert on every event, event though i set it as None and in Settings, it defaults to None, and the third problem was that my data entered on my iPhone wasn't syncing to anything, it was only on the phone, so no back up.)
It's been very buggy and crazy. i just listed the problems that happen consistently. There are others that happen sporadically.
The thing for me is that i only use the iPhone calendar, and occasionally i will use iCal if it's more handy.
I DO NOT use Google Calendar, or any other 3rd party calendar.
The reason i think i have had the GMT problem (and the other two) is because one of my Apple IDs (i have at least two) which is my main one that i use for everything except logging into iCloud, is a gmail.com email address. The iCloud email address is identical to the gmail one on the left side of the @. Maybe that confuses OS? all i can do it speculate.
Anyway, so because my main apple ID and my main email address have for years been the gmail user name and email address, i have always had that in my Calendar settings on the iPhone as my default calendar. I didn't know this until this GMT thing came up. I never knew there WAS a default calendar setting. In trouble shooting the GMT/30 minute alert/not syncing data problem, i learned that i have a default calendar setting and that in my case (not on everyone's iPhone but on mine at least) there are multiple possibilities for default Calendar. The top one, in the order they're presented, is iCloud. Under the heading, iCloud, it has a list of sub calendars, Finance, Family, Work, etc. Any one of those can be selected as default calendar. Or, the second heading is my gmail email address, and under that heading is my gmail user name (which is my actual name). It's the same as my iCloud user name, so again, maybe that confuses OS8.
Anyway, because i only use the Apple calendars and not Google Calendar or any other 3rd party calendar, i figured out that i don't need to have my gmail address set as my default calendar, although i would prefer to, but it really makes no difference that i can see. So, i created a generic name iCloud subcalendar (AllCloud) and set that as my default calendar. That immediately got rid of the three problems, unwanted GMT info, unwanted 30 minute alerts, and failure to sync. So i don't have any of that aggravation, but still want to know when the problem is fixed and also want to understand the problem better. I think it has something to do with iCloud and some change that was made with the OS8 code that has disconnected iCloud from gmail and Google and 3rd party Calendar programs which previously worked fine with iCloud.
I have asked this question before on this thread but haven't seen an answer, unless i missed it (so may posts, so little time). My question is, is there something superior about Google Calendar that would prevent people from switching their default calendar to an iCloud calendar, which would get rid of GMT info? I understand that some people have to use Outlook calendar related to work/their job. If not 3rd party calendar is not required, what are the reasons for staying with it, for people who suffer, some quite terribly, with these OS8 calendar problems?
I would like to ask what your default calendar setting looks like. My daughter has an iPhone and no 3rd party calendar. In her settings, there are only the iCloud calendars. I have what i described above.
I am wondering if people who use Google calendar as their default calendar (in the iPhone calendar settings) switched to an iCloud calendar for default, what would they lose? Would they lose all their Google calendar data? I mean, it would still be on Google Calendar, if entered there on the computer, but if entered on the phone, what would happen?
Sorry for your ordeal. I feel so fortunate that i don't use or need Google Calendar or another 3rd party calendar. I don't know the advantages of using Google calendar over using an iCloud calendar but there must be many for people to continue to live with these terrible problems caused by iOS 8.