The official Pokémon movie website has updated. Translations follow:
Media Information
Magazines:
Monday April 15th: "Corocoro Comic" - The latest news & information on the pre-screening
Saturday April 20th: "Corocoro Ichiban!" - The latest news & information on the pre-screening
*Note that these are the scheduled publication dates, and as such are subject to change without notice.
Source:
https://www.pokemon-movie.jp/news/?p=3618