It's like people don't read no matter how often they shove it in our faces...

In order to accompany Patch 3.3 as well as infrastructure maintenance, we will be performing maintenance on all Worlds at the time below. During this period, FINAL FANTASY XIV will be unavailable.

in·fra·struc·ture
/ˈinfrəˌstrək(t)SHər/
noun
noun: infrastructure; plural noun: infrastructures
the basic physical and organizational structures and facilities (e.g., buildings, roads, and power supplies) needed for the operation of a society or enterprise.

main·te·nance
/ˈmānt(ə)nəns,ˈmān(t)nəns/
noun
noun: maintenance
1. the process of maintaining or preserving someone or something, or the state of being maintained.


TLDR
They unplugged the servers to do physical maintenance on them. Of course we cannot update yet.