The Munich ChronoType Questionnaire (MCTQ) has now been available for more than 15 years; its original publication has been cited 1,240 times (Google Scholar, May 2019); its online version, which was available until July 2017, has produced almost 300,000 entries from all over the world (MCTQ database). The MCTQ has gone through several versions, has been translated into 13 languages and has been validated against other more objective measures of daily timing in several independent studies. Besides being used as a method to correlate circadian features of human biology with other factors – ranging from health issues to geographical factors – the MCTQ gave rise to quantifying old wisdoms, like “teenagers are late” and has produced new concepts, like social jetlag. Some like the MCTQ’s simplicity and some view it critically; it is time to have a self-critical view on the MCTQ, to address some misunderstandings and give some definitions about MCTQ-derived chronotype and the concept of social jetlag.