You can view staff members who have left or joined within the last 6 months by going to Reporting > Reports > Staff (tab) > Contracts.
If you want to check staff who have left, you will need to click onto "show inactive staff members" and "show expired contracts".
Once you have run the report, click onto the contract end date heading twice (anywhere apart from the bin) and this will filter the report to show the most recent leavers.