Time meant everything to Severus. Or rather, timing. How fast one reported to the Dark Lord after being summoned, for example, marked if, and how long his eye stayed upon you at the beginning of the meeting. Quick responses meant a nod of acknowledgement and perhaps escape from a capricious Cruciatus. Lateness meant the same nod but with a marking glance, and your nerves would inflame as the curse lit you up from the inside. Voldemort did not tolerate excuses, though it pleased him, on occasion, to hear them as his victim's body writhed before him.
Dumbledore too, had been a stickler for time. He sighed and thanked Merlin he was a Potions Master, wherein time could mean success or failure in his day to day work of creating tinctures, salves, and pastes for the school as well as other businesses he kept supplied in his free time.
A snort echoed through the lab. Free time was not something Severus ever had. Every minute that passed, every chime that came from the school bells, or the clock on his mantel, was marked for someone else. Frankly, he looked forward to death's silence, when he no longer he pulled between two masters, one of them dead and still managing to pull his strings.