We don't use the word "finally" in titles gratuitously on Android Police, but this instance warrants it. For years and years, we've heard the same complaint when covering Google Calendar: you can't change an event's calendar on the Android app. You need to use the web app or if you're bound to your phone, you have to delete the event from one calendar and manually create another in the second one. The update to version 5.8.18 of Calendar solves this issue by adding two new options: copy and duplicate. Sadly, moving an event from one calendar to another still seems to elude the team...
But let's not be grumpy and instead appreciate what we just got. Tapping the overflow menu of any calendar item previously only let you delete it. Now there are options to duplicate it or copy it. Duplicating creates a similar item in the same calendar but opens it in the editor so you can still make changes before saving it, including choosing another calendar. Copying just shows a pop-up menu with your other calendars so you can choose which one it gets copied to, then it opens it in the editor so you can also make changes before saving. I'm not sure why these two needed to be separate actions. A move function would make a lot more sense along with copy.
The other change in this version of Calendar is the option to email guests when you make changes to an event.
• Copy and Duplicate - Copy an event from one calendar to another, or duplicate an existing event to use it as a template for a new event.
• Notify guests - Choose whether to email guests when you update an event.
If you're impatient to get this new copy/duplicate option, version 5.8.18 of Calendar is the one you're looking for. It's been rolling out over the past few days but it hasn't reached everyone just yet so you can grab it from APK Mirror to install it manually.