How your inner clock is influenced

You are not a slave to your circadian rhythm and can actively influence it. To prevent the near-24h circadian rhythm to shift away from actual daytimes over time, it synchronizes to certain exogenous (external) time cues. These so-called zeitgebers (from German “giving time”) phase-advance or phase-delay circadian rhythm, depending on the stimulus and the time of stimulation [Roenneberg2007]. The dominant zeitgeber is light, but also factors like exercise, food intake or exogenous melatonin have been shown to impact circadian phase. Just like artificial light in the evening can delay your circadian clock, you can seize e.g. morning light exposure to actively advance it:

Light as zeitgeber

Physical exercise as zeitgeber

Nutrition as zeitgeber

Melatonin as zeitgeber

Temperature as zeitgeber

Sound as zeitgeber