Regular Expeditions occur in the game, but they're only open for a limited time.

When a new Expedition is about to begin, you'll receive a notification.

Once an Expedition is available, its icon will show up on the right side of the screen. Click on this icon and hit the "Start" button to begin the Expedition.

During an active Expedition, a timer will be shown on its icon, indicating how much time is left for you to participate.

Once the timer runs out, the Expedition will end, and you won't be able to join it anymore.

You can only complete tasks, claim rewards, and explore areas while the Expedition is ongoing.