All raid instances reset at a certain server time on certain days, regardless of when players were actually saved to the instance. The reset times are as follows:
Blackwing Lair: Every 7 Days during weekly maintenance Molten Core: Every 7 Days during weekly maintenance Temple of Ahn'Qiraj (40-man): Every 7 Days during weekly maintenance Naxxramas: Every 7 Days during weekly maintenance Onyxia: Every 5 Days at 4:00AM Zul'Gurub: Every 3 Days at 4:00AM Ruins of Ahn'Qiraj (20-man): Every 3 Days at 4:00AM
