To a first approximation, it is more important that some tasks be regularly attended to, than how often they are attended to. For example, it’s important to brush your teeth, and many people follow so-called proven recommendations of attending to it three times a day. Cope’s dentist recommends that if he does it really well, he needs to do it only once a day. Dina has learned that it is twice a day. What is important is that all of these recommendations have a rhythm, and as such, they lead to habit formation in human beings. By making events such as eating, or brushing your teeth, or planning upcoming work habitual we can relieve the team of focusing on when, so they can focus on what. So in Scrum it is best to first establish a cadence, and then to adjust the frequency and duration of each event as you inspect and adapt.
Rhythm is a strong and pervasive foundation of human existence. Hall, in his book Dance of Life, says, “I am convinced that it will ultimately be proved that almost every facet of human behavior is involved in the rhythmic process.”  Eviatar Zerubavel notes that we are governed on one hand by cycles of nature, such as going to bed every night, and on the other hand by cycles of the “machine,” such as business and delivery schedules.  Sometimes there is ambiguity between them, such as in the length of a Sprint, which is about a month long by default — month coming from the same root as the word moon. Natural rhythms tend to be periodic and happen of their own accord.
To the degree we can tie our Scrum production rhythms to other “natural” rhythms and their events, they can serve as sentinels and reminders of the associated impending Scrum activity. So Daily Scrums happen daily, on the cycle of the Earth’s rotation; Sprints tend to follow business cycles which, from a Scrum perspective, are part of what people accept as being the more natural ecosystem within which Scrum is embedded. (Of course, those business cycles may loosely follow truly natural cycles in their own right: see Follow the Moon.) In general, there is a strong interweaving of the time and process aspects of Scrum as emphasized here in the Value Stream Pattern Language, with the comings together of people that are the focus of the Product Organization Pattern Language. Scrum events are configurations of space (relationships between people) in some context of time (an event).
Scrum features many patterns based on rhythm. All Scrum events (Sprint Planning, Sprint Review, Sprint Retrospective, the Daily Scrum) are based on rhythms. Organizational Sprint Pulse aligns multiple teams around a common rhythm. Having these events recur regularly on a known cadence avoids the waste of having to repeatedly find time for them.
Rhythm and time-boxing are two sides of the same coin. Sprints might start every two weeks; that means that a Sprint is no longer than two weeks.
Scrum’s rhythms come from long experience and are to some degree prescribed: for example, the Scrum Guide  says that a Sprint may not be longer than one calendar month, and it typically is no shorter than a week. A great Scrum Team matches the actual duration of a cadence to yield the most output, or comfort, or predictability, or other desirable trait. In most Western cultures, when we sit together at lunch at work, some people finish consuming their food in 7 minutes and some take 25 minutes. But we sit there together for 30 minutes and then, as though on cue, we go back to work. We find built-in clocks that balance our social needs. The cadence serves that social need rather than vice-versa. And different cultures have different social needs: these lunchtime synchronization intervals may change or nearly disappear the nearer a culture is to the equator. Scrum does not presume that one size fits all, and it is up to each team to find their place within the recommended range (or sometimes, outside that range) that works best for them.
Iterations are also fundamental to Scrum, and iterations work best if they follow a cadence.
Good kaizen often has roots in sustaining a good rhythm. Just as daily cycles reinforce brushing your teeth, so the natural cycles of the day, business week and month can reinforce good practices that align with them. This fits into the notion of intentional practice in One Step at a Time.
Hall invented the term monochronic to describe cultures that are attentive to linear time and rhythms. The Swiss are the stereotype of a monochromic culture. And Hall uses the word polychronic to describe cultures based on a shared model of multiple simultaneous time streams: the usual stereotype here is Mexican culture. So, in a monochronic culture, one queues at the doctor’s office and people take appointment times seriously. In a polychronic culture, the doctor may come into reception and spend a little bit of time with each patient before seeing them in the examining room. Monochronic cultures focus on the process of the whole, while polychronic cultures are more concerned with the individual. While the gross Scrum framework is monochronic and based on rhythms as described above, work within the Production Episode is highly polychronic: everyone doing everything all the time. Most development cultures, rooted in indigenous and corporate norms, may struggle a bit with adopting one or the other of these styles of working. Such adjustment is part of the deep learning necessary to mastering agile development while meeting market needs.
 Edward T. Hall. The Dance of Life. New York: Bantam Doubleday Dell Publishing Group, re-issue of 1988, p. 153.
 Sally Helgesen. Everyday Revolutionaries: Working Women and the Transformation of American Life. New York: Doubleday, 1998, p. 140.
 Ken Schwaber and Jeff Sutherland. The Scrum Guide. http://scrumguides.org, accessed 13 November 2017.