If you're still digging up fossils and presenting them to Blathers as part of your daily Animal Crossing: New Horizons routine, today you might want to hang around the museum a bit longer. Today marks the start of New Horizons' International Museum Day event, and though you'll have until the end of the month to wrap it up, you can complete it a lot faster than that.
For this limited time event, you'll need to have the museum built but don't need to have the art gallery wing added after Redd's recent addition to the game. For International Museum Day Blathers is holding a stamp rally through the museum's three other sections. Complete the rally activity in each section and you'll receive a corresponding bug, fish, and fossil plaque to hang up in your home.
Even though the event lasts until May 31, like the May Day event before it, this is more of a one-and-done affair. Once you've got those plaques, that's all. It's essentially incentivizing players to check in on the state of their museums, which is worth doing on a regular basis anyway (cool exhibits aside, you might run into your villagers there and see some special museum-only dialogue).
With another short, low-impact activity here, it's looking more and more like the 12-day long Bunny Day celebration was a serious outlier in terms of what to expect from New Horizons' events. For folks who are still sinking a few hours or more into New Horizons every day, there's probably a happy medium to be found between a nearly two week long event that disrupts the whole crafting loop and these short little distractions. On the other hand, if your island enthusiasm's starting to wane, then these little events are probably the perfect length.
In June, we know New Horizons is set to have a Wedding Season event available for the entire month, accessible via Harv's photo studio island. Beyond that, there's no word on what other special events or updates are coming to New Horizons, so hopefully we'll get another dispatch from Nintendo on what to expect soon. As with all things game dev right now, it's also possible that the COVID-19 pandemic has thrown a wrench into future New Horizons updates—Nintendo hasn't publicly announced specific delays yet, but a recent report indicates that there'll be no Nintendo Direct next month due in part to the impacts of work from home.