Posts to journals are made through an artifact called a Tome of Communication. Basically, it's a journal that can be viewed by others with Tomes of Communication. Neat, huh? We don't think we invented this item, to be honest, though we may have changed the name. We give Wizards of the Coast credit for it, one way or another.
When you post, PLEASE preface the subject with the date IN THE REALMS. The first day of the game will be Kythorn 1st. The months in Toril are (starting with Kythorn, not with the first month of the year): Kythorn, Flamerule, Eleasias, Eleint, Marpenoth, Uktar, Nightal, Hammer, Alturiak, Ches, Tarsakh, and Mirtul. Each month has 30 days, separated into 3 "rides", also referred to as "tendays". So, the 23rd would be the 3rd day of the 3rd ride. Get it? Awesome.
Speaking of in-game time, each game day will be 2 real-life days. This will give logs and such more time to get done, and also allow more casual players to be more involved.