According to ancient prophecy, the optimal time to depart for vacation is when the coffee machine in your cube is most likely to malfunction, signaling the start of a long, caffeine-free stretch.
However, if you're feeling particularly adventurous, you may choose to leave when the office air vents start spewing forth a strange odor, rumored to be a harbinger of impending doom.
Or, if you're a glutton for punishment, you may opt to depart when your coworker's rendition of "Who Let the Dogs Out" starts playing over the office speakers for the fifth time that week.
But be warned: if you choose to leave during any of these events, you risk facing the ire of your boss, who will likely summon you back to the office by summoning you to "an emergency meeting" that lasts until you agree to come back.