interesting... that sounds a littlell umm wierd
what happens when they win a siege? can they sign up again?
Oddly enough, varied/multiple siege times has been one of the most requested changes over the past two or three years.
As far as I have been able to determine, any given guild may siege *once* per day, with a 10-hour cooldown between siege signups. At least, the 10-hour restriction was displayed after our siege this afternoon.
With my specific time zone (Central) in mind, the first siege started a 3pm CDT--registration "opened" no later than 1PM CDT, siege prep is at 2pm CDT. The next registration for those guilds which did not sign up for the first siege starts at 5pm CDT, closes at 6pm. Siege prep is 1 hour after registration, siege follows 1 hour after siege prep. Siege lasts 1 hour, so the next registration (3rd siege) should be at 8pm CDT.
If my math is correct, sieges are at (Central time) 3pm, 8pm, 1am, and 6am. Registrations would begin at 1pm, 5pm, 11pm, and 4am. Maybe.

My math could be off, since there's a large gap between the 6am siege and the 1pm registration for the following siege.
We may have to wait and see how this all plays out.