BirthdaysPage editor: Belinda Hobbs
On July 30, 2004 the Wizard of the Month calendar changed to say Happy Birthday to Neville Longbottom. The next day, July 31st, it (of course) said Happy Birthday Harry Potter. These were the first birthdays displayed and started a year of anticipation as we watched the calendar for more birthdates! Over the course of the next year 19 birthdates were announced (20 if you count both Weasley twins), the last new one being Dobby on June 28, 2005.
Besides the birthdates, there is more canon information we can gather from these.