Having Trouble Typing? What on Earth Is Chronotype?

In this commentary (which is by no means a review of chronotyping), I try to clarify the distinction between 2 different ways of assessing chronotype by questionnaires. The morningness/eveningness questionnaire (MEQ) determines daily preferences producing a score, and the Munich ChronoType Questionnaire aims to determine phase of entrainment producing a time. An understanding of the MEQ requires knowledge of its history. Although both have their respective validity, they mean very different things and should be used appropriately in studies with different aims and questions. Although they show correlations in population comparisons, they should not be amalgamated when reviewing the literature.