Ambassador Amnerys posted on the official forums:
We will bring the Free Realms servers offline on Thursday, March 28, 2013 at 8:00 a.m. PDT (San Diego Time) for a Game Update. Anticipated downtime is around 1 hour.
This update will bring some spring fun, and hey...isn't time about time for a Birthday Bash??
Our Birthday Bash guides from years past can be found right here!