Contextual suggestions in Google Messages aren't new. The app can already offer up stickers, Assistant recommendations, smart replies, and some actions while you're talking to your contacts, and it's that latter ability that seems to be expanding. Among the new actions, Messages can now propose adding a calendar event when you bring up a specific time and date during a chat.
If you've enabled Suggested actions in Messages (in the app's Settings > Suggestions in chat), you should start seeing a new pop-up when you send a text mentioning dates and/or times. The Create event pill lets you quickly switch to a pre-filled Google Calendar event with the date, time (including a one hour duration by default), and a small note saying "This event was created from a message." All you have to do is save it and this will be added to your schedule, without much work on your end.
The feature is certainly a handy time-saver, but it's not the only new smart action we've spotted. The Messages app already shows a few example pills of these in its settings menu, and we've come across the location sharing and recent photo attachment suggestions before. However, we think the "Haha GIFs" and "Start video call" ones are new (none of us have encountered them before), though triggering the latter took a lot of tries. Eventually, it was such an unconventional wording that got the pill to pop up, proving the robots aren't all that smart yet.
Google pinky-swears that these are generated on-device and not sent to its servers.
These new suggestions started showing up for some users on v7.2.203 and 7.2.204 beta of Messages, however they don't appear to be available to everyone. Despite being on the same version, everything I try fails to trigger them (even in RCS chats), so I guess the server-side switches are at play here too. You can try speeding up the process by grabbing the latest beta version from the Play Store or APK Mirror.