Bring guests by the BioPop lab and turn off the lights even just one hour earlier than usual and the show will be muted, he and others who work there say. (Though apparently some can get it together better than others.) Expect the dinos to perform on demand after a long journey to another time zone? Forget it.

Like humans, dinoflagellates follow a roughly 24-hour circadian cycle triggered by phases of sunlight. Unlike humans who may find ways to mask their irritability, sleepiness or lack of concentration, dinoflagellates are very direct about their inability to perform when their schedule is out of whack: They simply won’t glow the same way. (A number of biologists who have helped advance our understanding of human sleep cycles made initial circadian breakthroughs with these organisms for connected reasons.)

Children can be similarly transparent, Dr. Deheyn points out.

“If there is still light out, it’s definitely not time to go to bed,” he said, likening his 6-year-old son’s experience with Daylight Saving Time to that of a dino with jet lag. “Even though you try to explain the time change to him, his body will react to the light. It’s only an hour. But it takes weeks to recover from that change.”

In the same vein, losing an hour is a big deal for reasons beyond lost sleep.

“Remember, we have clocks in every organ in our body,” said Robert Thomas, the director of a sleep medicine fellowship at Harvard’s Beth Israel Deaconess Medical Center. Any kind of shift, small or large, means, “You’re not just moving sleep —you’re moving your entire body. It’s like a giant ocean liner. A big ocean liner slowly chugging away. You can’t just jerk it around.”

Dr. Thomas, who also runs a sleep lab focused on helping individuals with extreme sleep disorders get on a more normal schedule, takes the impact of light seriously in his home as well. Every night at 8 p.m. he turns off all the lights so as to avoid the risk of pushing his circadian system into another time zone. Because we talked on the phone closer to 9, this meant his end of the conversation was conducted in complete darkness.

“If jet lag was permanent, it would probably kill us,” he said.

But in the grand scheme of circadian disruptions, a biannual shift in an hour is not the end of the world for humans — or dinoflagellates.