They just switched back to the 180 days.
The online system is very temperamental. Some days it works fine, others it doesn't.
What I would do on the day your booking window opens is try to make them online, whenever it is that the system will let you...I've heard anywhere between 3am-6am. Then if doesn't work, call when the phone lines open at 7am. That's what I had to do last time I made ADR's.