The Magearna event is a QR Code so it never ends (NOTE: you have to beat the E4 and Kukui before using the code).
As for the Munchlax + Snorlium Z event, it already ended on January 11th. Sorry that you missed it.
Hope this helps :)
Magerna: No, and it never will!
Munchlax: Yes. It passed by 2 months ago.