Explorations will remain "active" two-weeks before and two-weeks after the reminder date set by a group administrator.
Note: Active dates only affect how long an Exploration appears on users' home pages. Users will still be able to submit work through Explorations even after the reminder date for an Exploration has passed. Active dates are also optional.
If you're unsure whether or not you can still submit work after an Exploration is no longer active, don't worry - you can!