Good event, very nice building, wish I could've gotten the full tablet set in a couple of my worlds, but that has been the way of that mechanic.
This calendar was much better than the one in the winter event, which I completely ignored. Part of this was because the daily prize could be swapped (which I thought was great) so it made it more likely that any day could have at least an ok prize, but the other part is the mechanic of this event. You could preload the next day by exploring ahead and leaving the 2nd gem to collect the following day which meant not as much wasted collection. As that could also be done with the urns (or ignore them completely) on days the daily and the swapped in alt were bad, that meant a lot more flexibility and therefore made completing the calendar quite feasible. (also, iirc the winter one required 10 lockpics for a missed day, which was ridiculous)
As I've said with the last couple events: I do not like the mystery box from the previous event being "required" to complete an event building. This event had enough flexibility that it technically wasn't but you did need one of: [mystery box, complete calendar or, maybe, full tablet set] to complete. I can see completing the calendar to be a bit much as missing more than a couple days would really lock that out, and the full tablet set was 50/50 at best, so basically, the mystery box was the safe guaranteed* completion.
*technically not guaranteed, but as close to that as one can reasonably expect to get.