The deadline is basically "your" local midnight. I tend to leave the FTP on for a wee bit after the last midnight of the 29th, just to be sure everyone gets a chance to upload.

Also, even if you entry is not finished, it's always nice to upload something. Having a bunch of entries half finished is much better than having absolutely nothing uploaded. And it doesn't look at bad. So please upload what you've done even if it's not finished. It shows that there was interest instead of nothing in it's place in the showcase after.