scheduling event publication

I do not succeed in scheduling an event publication in a date different from the one of the event itself.
I mean: today, March the 25th, I prepare the event page for an event starting on May the 1st but I want to publish it on April the 15th so, instead of publishing it immediately, I choose to modify the date in the proper WP panel, but the event publication date is always 1st May. No problem if I decide to publish the event immediately: it is correctly published.
Any solution or bypass?
Thanks in advance
sandra