Chronotypes: What They Are and How to Figure Out Yours

One of the most overlooked reasons people struggle with sleep is timing—not habits. Humans are not all wired to sleep and wake at the same hours. This variation is known as chronotype, and it influences when you naturally feel alert, hungry, focused, and sleepy.

If you’ve ever felt that sleep advice “should work” but doesn’t seem to fit your body, your chronotype may be part of the explanation.

By Luca Olsen
SemiPremium founder, sleep expert                                                      Published 29.1.2026
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What Is a Chronotype?

A chronotype describes your natural tendency toward earlier or later sleep and wake times. It is influenced by:

  • Genetics
  • Circadian rhythm timing
  • Light sensitivity
  • Age

Chronotype is not a preference. It is a biological inclination.

Trying to force yourself into a schedule that conflicts with your chronotype often results in:

  • Prolonged sleep onset
  • Fragmented sleep
  • Morning grogginess
  • Evening alertness at the “wrong” time

This mismatch is sometimes referred to as social jet lag.

The Main Chronotype Categories

Chronotypes exist on a spectrum, but they are often grouped into four broad categories.

Early Chronotype (“Morning Types”) Often called “larks.” Common characteristics:

  • Naturally wake up early
  • Feel alert soon after waking
  • Become sleepy in the early evening
  • Struggle with late nights

Intermediate Chronotype The largest group. Common characteristics:

  • Flexible sleep timing
  • Moderate morning alertness
  • Gradual evening wind-down
  • Better adaptability to schedule changes

Late Chronotype (“Evening Types”) Often called “owls.” Common characteristics:

  • Difficulty falling asleep early
  • Peak alertness in the evening
  • Struggle with early mornings
  • Often mislabeled as undisciplined

Very Late Chronotype (Delayed Sleep Phase) At the far end of the spectrum. Common characteristics:

  • Very late natural sleep onset
  • Difficulty waking at conventional times
  • Normal sleep quality when allowed to follow natural timing
  • Frequently mistaken for behavioral insomnia

Chronotype Is Strongly Influenced by Genetics

Chronotype is not random. Large genetic studies have shown that a significant portion of chronotype variation is heritable, with estimates ranging from 40–50%. Multiple genes involved in circadian timing, including clock genes such as PER, CRY, and CLOCK, contribute to whether someone tends toward earlier or later sleep.

This means that for many people, chronotype is not something they “developed”—it is something they were born with.

An Evolutionary Theory: Why Not Everyone Slept at the Same Time

One compelling—though not definitively proven—theory is that chronotype diversity served an evolutionary advantage.

Anthropological and evolutionary researchers have proposed that in early human groups, staggered sleep timing increased survival. If everyone slept at exactly the same time, groups would have been more vulnerable to predators, environmental threats, or rival groups.

Instead, variation in chronotypes may have ensured that:

  • Some individuals were alert later into the night
  • Others woke earlier in the morning
  • The group as a whole was rarely completely unguarded

This idea is sometimes referred to as the “sentinel hypothesis.”

Importantly:

  • This is a theory, not a proven fact
  • It is supported indirectly by genetic diversity in circadian traits
  • Similar staggered vigilance patterns are observed in other social species

From this perspective, late chronotypes were not “problem sleepers”—they may have been night sentinels.

Why This Matters Today

Modern society is built almost entirely around early chronotypes. Work schedules, school start times, and social expectations often assume:

  • Early rising
  • Early productivity
  • Early sleep onset

For people with later chronotypes, this creates chronic misalignment. The result can look like:

  • Insomnia
  • Poor sleep quality
  • Persistent fatigue
  • Nighttime alertness followed by morning impairment

In reality, the issue may not be sleep ability—but biological timing in conflict with social structure.

The Danish B-Society: Advocating for Type-B Personalities

In Denmark, this societal bias toward early risers (often called "A-persons" or morning types) inspired the creation of B-Society (B-Samfundet), a grassroots organization founded in the mid-2000s to champion the needs of "B-persons" — late chronotypes or evening types who naturally thrive later in the day.

The group argues that modern schedules (early school/work starts, rigid 9-to-5 norms) discriminate against owls, leading to lower productivity, poorer health, and unnecessary stress. They highlight research showing late chronotypes perform worse in early-morning settings and push for practical changes: flexible start times in schools and workplaces, later school hours for teens (where evening types dominate), and greater societal respect for biological diversity in sleep timing.

B-Society's efforts represent a political and cultural attempt to make room for type-B personalities in a world designed for type-A. By raising awareness and lobbying for policy shifts, they've sparked international discussion about how chronotype mismatches contribute to "social jet lag" and why forcing everyone into the same rhythm harms well-being.

How to Figure Out Your Chronotype (Without a Quiz)

You don’t need a questionnaire to gain insight into your chronotype.

Step 1: Observe Sleep Without an Alarm On free days or vacations:

  • Go to bed when genuinely sleepy
  • Wake naturally
  • Repeat for several days

Note when sleep feels easiest and most restorative.

Step 2: Identify Consistent Patterns Ask yourself:

  • When do I feel most alert?
  • When does sleep come naturally?
  • When does forcing sleep fail?

Ignore obligations. Focus on biology.

Step 3: Pay Attention to Evening Alertness Evening alertness is one of the strongest chronotype signals.

  • Rising alertness late at night suggests a later chronotype
  • Early evening sleepiness suggests an earlier one

Step 4: Notice Light Sensitivity Late chronotypes often:

  • Feel stimulated by evening light
  • Struggle with early morning light exposure

Early chronotypes often experience the opposite pattern.

Chronotype vs Insomnia: A Crucial Distinction

Chronotype mismatch can mimic insomnia. Signs include:

  • Difficulty falling asleep at imposed bedtimes
  • Sleeping well on free days
  • Feeling alert late but exhausted early

Recognizing this distinction can prevent years of unnecessary frustration.

What Can Be Changed — and What Can’t

Chronotype can be shifted slightly, but not fundamentally changed. Helpful strategies include:

  • Morning light exposure
  • Consistent wake times
  • Reducing late-evening light

Unhelpful strategies include:

  • Forcing early bedtimes
  • Fighting alertness
  • Self-blame

Working with your chronotype tends to be more sustainable than fighting it.

One practical way to reduce disruptions and support better sleep onset—especially when your chronotype means you’re naturally more alert later in the evening—is to minimize direct screen interaction and blue light exposure during the vulnerable wind-down window. A dedicated remote controller for smartphones such as SemiPremium allows users to control volume, pause, skip tracks, or manage playback with physical buttons from under the covers, without ever touching the screen or lighting it up. Read more about SemiPremium here. By keeping the device face-down, dark, and at a safe distance while still accessing its audio or queued content (podcasts, audiobooks, white noise), this approach preserves melatonin production, prevents accidental bright flashes from notifications or ads, and avoids the cognitive and physical arousal that comes from handling the device. It turns a potentially sleep-disrupting habit into a low-stimulation one, helping maintain the natural downward progression of arousal needed for smooth sleep onset—regardless of when your body clock prefers to start the night.

Final Thought

Chronotype diversity is not a flaw. It is a biological feature—possibly one that once protected us.

Understanding your chronotype won’t solve every sleep problem, but it often explains why effort alone hasn’t worked. And for many people, that understanding brings real relief.

Explore more in the Sleep Onset Toolbox for strategies that work with your biology instead of against it.

Your internal clock isn’t broken—it’s just running on a different schedule.