How Erminig works :
Google Calendar is the reference calendar. Its contains all events.
Gpe contains only events between the days range specified in the profile.
Today : 07/06/13
Erminig profile :
previous days: 2
next days : 2
So, Erminig will import events from Google to GPE, the events between 07/06/11 and 07/06/15
The GPE database is always cleaned and contains only the days range events.
All modification in GPE are replicated in Google.

Updating process :
1 - Deleted GPE events are deleted in Google Calendar
2 - New GPE events are created in in Google Calendar
3 - Updated GPE events are modified in Google (changing title, location, etc ...)
4 - All events in Gpe calendar are deleted
5 - days range Google events are imported

It's very difficult to code an advanced replication.
I have no idea to do it with an easy method.

If someone can write this in good english, I will add this to my website.

Sorry, for your GPE calendar.
If You extended the date range in the Erminig profile, You will get all your events.