Using the copulation times from 78 White married women, representing an average of 72 reporting days per woman over a 12-month period, two expected prominent copulatory rhythms were found and described quantitatively. The daily rhythm is characterized by a major evening peak, which encompasses 58% of the daily copulations, and a minor peak in the morning. The weekly rhythm describes a rather constant copulatory rate during weekdays, with a large increase on weekends. The probability of orgasm was found to be significantly greater in copulations taking place after midday. Because of the long-time speculation that the moon plays some role in the timing of human love-making, the data were examined for such a relationship. None was found.
Palmer, John D.; Udry, J Richard; and Morris, Naomi M.
"Diurnal and Weekly, But No Lunar Rhythms in Human Copulation,"
1, Article 13.
Available at: https://digitalcommons.wayne.edu/humbiol/vol54/iss1/13