Having a standard set time for all Starfleet ships is a necessity for the sake of communication and synchronicity, however it does make it challenging for the crew when they land on a planet where days pass differently than they do onboard. This is dually true for moments when the ship lands on the daytime side of a planet while it is nighttime onboard, and the crew can often suffer serious jet lag or an interrupted circadian rhythm. For Spock, who grew up on a different planet than the one their artificial time is based on and has a circadian rhythm built to Vulcan rather than Earth, watching the crew groggily wade through a new timezone is like sweet sweet justice.