I use Outlook for my calendar and don't think I've ever used Google calendar. However, I want my Outlook calendar to sync with my Android phone (anti-Apple person here) so to do this, I had to sync Outlook with a Google Calendar, which in turn syncs with my phone. Basically anytime I am out and add something to my phone calendar, it automatically adds it to my Outlook calendar, and vice-versa. The good thing about this, is that since this process uses the Google calendar to sync the 2, Echo recognizes that and Echo sees my Outlook calendar. (It sees the Google Calendar that my phone and Outlook use to sync each other with) - I use gSyncit which is an Outlook add-on, to do this. It's fairly inexpensive. I think maybe $20? There's a free version but it's limited. It also syncs your tasks and contacts as well though. Hope this helps!
+tek