- Before importing, send request with all UIDs to the server. (or maybe not all but 50 at a time) - If it doesn't give a 404, parse the calendar-data from the server and compare the LAST-MODIFIED and SEQUENCE-properties of both. - If the version, the user wishes to import, is newer, update the event on the server. <bountysource-plugin> --- Want to back this issue? **[Post a bounty on it!](https://www.bountysource.com/issues/81351964-import-check-if-uid-already-exists-check-which-one-is-newest-and-update-if-necessary?utm_campaign=plugin&utm_content=tracker%2F45525646&utm_medium=issues&utm_source=github)** We accept bounties via [Bountysource](https://www.bountysource.com/?utm_campaign=plugin&utm_content=tracker%2F45525646&utm_medium=issues&utm_source=github). </bountysource-plugin>