Biological Clock Day
Biological Clock Day is held on April 28. This event in the third decade of the month April is annual. 
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Circadian rhythms are physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism’s environment. In fact, light is the external factor that affects our circadian rhythm the most.
It’s not just sleep-wake cycles that are cued in. Body temperature, heart rate, blood pressure, and stress regulation hormones are tied to these rhythms.
Our biological clocks drive our circadian rhythms. These internal clocks are groupings of interacting molecules in cells throughout the body. A “master clock” in the brain coordinates all the body clocks so that they are in synch.
Similar holidays and events, festivals and interesting facts
Babe Ruth Day on April 27 (On April 27, 1947, Babe Ruth attended Yankee Stadium for Babe Ruth Day. It was to be the second last time he was at the stadium);
Go Birding Day on April 27
Morse Code Day on April 27
Save The Frogs Day on April 27
Sense Of Smell Day on April 27
Tell a Story Day on April 27
World Tapir Day on April 27
National Pet Parent's Day in US on April 27 (Last Sunday in April);
International TableTop Day on April 27 (Celebrate on the last Saturday of April);
Freisen Medieval Market on April 27
Kiss Your Mate Day on April 28
Cubicle Day on April 28 (Designed by Robert Propst and known for a complete absence of individuality, cubicles were first introduced in 1967 as a way to subdivide open office space and provide workers with a degree of privacy);
Great Poetry Reading Day on April 28
Zipper Day on April 29
World Wish Day on April 29
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