At the following time, to fix issues with the Eternal Bond reservation system, we will be performing emergency maintenance on all Worlds. During this period, FINAL FANTASY XIV: A Realm Reborn will be unavailable.

I'm guessing in their internal testing they found a bug with the booking system and wanted to get it fixed before the system is active tomorrow.

You still can't schedule anything at the moment.

Somehow I doubt they will change the systems without giving people advanced notice, since this involves real money.