I've yet to use the word "reliable" with the topic at hand. But there are apps for this such as http://www.windowsphone.com/en-us/store/app/gcalendar/995b85c0-d7d8-450c-afa0-32497c7006f3
I'm sure there are others.
I plan to buy a new phone soon - the problem is that I would really like to buy a Lumia (preferably 925/920), but since I daily use Gmail for my work, I need a phone that could manage (read/add/update) Google Calendar events and Gmail Tasks. Are there any reliable apps for that in Windows Phone 8?
Thanks a lot in advance