Hey
Players need to manually check the calendar to receive a checkmark.
If you feel like you've done so and still remains a bug.
You may file a ticket towards Oasis explaining the situation.
To file a ticket. Click "Support" on either the client or browser.
To make the process faster, Include the following
Screenshot of your client/Server time/PC time and the calendar.
Plus your UID.
They can check and assist if it's indeed a bug or not.
Hope that helps.