When listing dates for (pretty much) any reason, always list the day. The day will help people remember. If I don't know what today is (it's the 4th), I certainly don't know when the 7th is, but I do know when Saturday is. So say "Saturday, April 7th, 2007" and I'll better remember that Saturday I should come listen to you play or come get my book signed or whatever it is you're listing the date for.
You should always list the year too, you never know what old web page they may stumble onto, you'll have some sad fans if they show up for something a year late.
Don't say tomorrow or today, when they read it later, today might already be tomorrow.