The official Pokémon movie website has updated. Translations follow:
Media Information
Magazines:
Saturday March 31st: "TV-kun" - Drawing contest notice, etc
Tuesday April 3rd: "Ciáo" - Pre-screening announcement
*Note that these are the scheduled publication dates, and as such are subject to change without notice.
Source:
http://www.pokemon-movie.jp/news/?p=3216