You can use the OpsProject web interface to archive your timesheet entries for a given timeframe. Arcived entries are saved to a different file from your current timesheet and you can no longer alter (or view) the archived entries in your timetracking client (ie Sunbird). Archived timesheets are available for reporting, for example through OpsAdmin or the OpsProject open office addons.
If you are an administrator you can check "arcive all calendars"
When you hit the "archive" button the jsp will call the OpsProject? server and tell it to archive your(or all) calendar.
It will return with a list of affected calendars.
Known Issues
When you archive a lot of calendars or the server just lacks the power to archive quickly some browsers will timeout. The pprocess of archiving is not affected by this but you will not see a page showing the outcome,