That was a very tough call we had to make by choosing this date. We kept it in order to respect the tradition. Who would we be if we break the rules on the third event :P
Yeah, I'm just complaining because - well, because that's what you do when you live in Paris :D Still, it might be an idea to start slowly moving the date earlier in the year - April has far worse weather and shorter days than June, so it is far better suited to indoors activities ;)
JS1k floats around March-April.
If the weather currently there is similar to the last days in Düsseldorf, it will not be that much different from April. :)
In April there is the Revision demoparty (the biggest demoparty in the world), it's not a good idea to collide with it.