Mondays really do make people blue, Friday is the happiest day of the working week and 'dull' midweek days are easily muddled up, according to a new study which found that the artificial seven-day cycle we live by shapes the way we think.
Psychologists from the universities of Lincoln, York and Hertfordshire created an experiment to test how our mental representations of days of the week are constructed and what effect this has on our perceptions of time.
They asked participants which words they most strongly associated with different days. They found that Monday and Fridays have a higher number of mental representations attached to them than their midweek counterparts - giving them stronger identities than Tuesdays, Wednesdays and Thursdays.
Conversely, these non-descript mid-week days carry less meaning, making them more easily confused with each other.
Mondays mainly prompted negative words like 'boring', 'hectic' and 'tired' and Fridays were associated with positive words like 'party', 'freedom' and 'release'.
Almost 40 per cent of study participants confused the current day with the preceding or following day - and most of those mistakes occurred during the middle of the week.
The number of mistakes rose to more than half when questioned during a Bank Holiday week, with people often feeling like they were a day behind.
Participants were also quizzed on how quickly they could recall the correct day, with people able to declare it is Monday or Friday correctly twice as fast as they could on a Wednesday.
"The seven day weekly cycle is repeated for all of us from birth, and we believe this results in each day of the week acquiring its own character," lead researcher Dr David Ellis, from the University of Lincoln's School of Psychology, said.
"Indeed, more than a third of participants reported that the current day felt like a different day, and most of those feelings were on Tuesdays, Wednesdays and Thursdays, reflecting the midweek dip in associations attached to different days.
"Our research implies that time cycles can shape cognition even when they are socially constructed.
"The Bank Holiday effect implies that apparent weekday is not determined solely by the seven-day period of the weekly cycle: transitions between the working week and weekend also play a role," Ellis said.
"One reason behind midweek days evoking fewer associations than other days could be down to how infrequently they occur in natural language, thus providing fewer opportunities for associations to form - for example we have an abundance of pop songs which make use of Mondays and Fridays, while the midweek days are rarely used," said Dr Rob Jenkins from the Department of Psychology at the University of York.
Jenkins worked on the study along with Professor Richard Wiseman from the University of Hertfordshire.
The findings have been published in the journal PLOS ONE.