Bernard's caught up in something much akin to how Dolores and Maeve experienced memory in Season 1 -- reliving past events. He's not sure what happened when, and because of his confusion, neither are we. It takes a while to get reoriented, and as the security team prods Bernard to tell them what happened, he flashes to the night of the party. If we start to get confused, the further Bernard dives into his memories, all we have to do is follow one simple thread: Is he wearing his glasses, or not? If he is, we're in the timeline immediately following the party/massacre. If he's not wearing them, then we're in the post-beach-wakeup timeline, and the lenses have been lost. Got it?
While that might help us keep track of the timelines for the first few episodes, it could ultimately prove to be Bernard's downfall. Once the humans around him get past their crisis mode, they might start to see something's off with how Bernard doesn't seem to need his glasses to read anymore, or prevent him from walking into the lab's glass walls -- and it's not like he had time to get LASIK surgery on the beach. Bernard, it could be time to claim you also use contacts. We hear they're all the rage in the future.