Menstrual cycle shortest and longest cycle lengths is considered very irregular. The average menstrual cycle lasts 28 days. The variability of menstrual cycle lengths is highest for women under 25 years of age and is lowest, that is, most regular, for ages 25 to 39. Subsequently, the variability increases slightly for women aged 40 to 44. The luteal phase of the menstrual cycle is about the same length in most individuals (mean 14.13 days, standard deviation 1.41 days) whereas the follicular phase tends to show much more variability (log-normally distributed with 95% of individuals having follicular phases between 10.3 and 16.3 days).
Menstrual leave employ such woman on days of the menstrual period." While Japanese law requires that a woman going through especially difficult menstruation be allowed to take leave, it does not require companies to provide paid leave or extra pay for women who choose to work during menstruation. In South Korea, not only are female employees entitled to menstrual leave according to the Article 71 of the Labour Standards Law, but they are also ensured additional pay if they do not take the menstrual leave that they are entitled to. In Taiwan, the Act of Gender Equality in Employment gives women three