Avoid event duplication when synching custom calendar to Google Calendar?

I have successfully saved all the events from my custom calendar to Google calendar with PHP script. But whenever i try to sync same calendar again, i see all the events are recreated & duplicated. Is their any Google Calendar API clue that might help开发者_运维问答 remove the duplication? Please help.

Regards.

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I am asuming you are using the iCal interface. We did a similar implementation a while back (not using php but anyways). What we used to keep this duplication away was that after we had created a new event in the google calendar we fetched from google and found this event. Then we keept track of the "CREATED" part of the iCal file that we got back from google, and simply used this as a reference to know both what have been synced and to be able to link items in google calendar and our side.