Mine would be SB-129 because of the weird time peroid (March 6, 2017 - March 6, 4017). Although if you consider the end of the episode, Squidward returns to the same day. Which means that although he froze himself earlier that day, he would have returned to work. Over the two thousand years, no one entered the freezer to get supplies needed to supply the Krusty Krab with its products, as the freezer contains frozen Krabby Patties. Otherwise, they would have seen Squidward in there. A theory of this episode is that there are two Squidwards for the rest of the SpongeBob series onward. One of which is still trapped in the freezer and will be for two thousand years, and the one who already was frozen for two thousand years, went back to the past, and then returned to the present. That is my opinion.