As to why they're doing such a long downtime this Tuesday, Erlendur S. Thorsteinsson, EVE's Software Director, jumped out to answer:
The original schedule called for a release in early Feb but there were issues in the localisation process that we had to sort out and then there was the the Alliance Tournament in early Mar. So 11 Mar it is. We used the extra time well for additional bug fixes.
Underneath the hood in EVE Online: Trinity 1.1 are massive database changes that will allow for more rapid and frequent delivery of new content in the future, such as new missions. Therefore we are doing an off-line backup of the database, like we do when deploying expansions, and that explains the start time.
Be sure to set extremely long duration learning up before you dock for Boost! Nothing quite so frustrating as losing time you could be using to get more skills -- and nothing quite so easily avoidable, either. If you're not sure what to do with your downtime and need your EVE fix, may we recommend that great Drone Bay podcast that we heard about?