This article identifies the cognitive processes associated with constructing a false date of birth (DoB) and explores how this might be used to identify and trace those who give a false DoB to police. A particular focus here is with asking people for their zodiac ‘star’ sign as part of an identification and verification process. A quasi-experimental research design was employed where 129 students were asked first to generate a false DoB, then a corresponding zodiac sign, subsequently describing the cognitive processes involved. The findings suggest that when generating a false DoB, people tend to either simply add/subtract one year, or add/subtract one month from their real DoB. When asked to give a corresponding zodiac sign for the false DoB given roughly 50% of people will fail this task. It is argued here that these findings should provide police with a way of tracing the putative offender from the false DoB they give as well as being able to identify date-of-birth liars face-to-face by simply asking them to provide a corresponding zodiac sign.