Period time: Time is a fundamental concept

Time is a fundamental concept in both science and philosophy, encompassing the past, present, and future. Whereas, a period is a specific span within time, marked by a start and an end point. List of time periods The categorization of the past into discrete, quantified named blocks of time is called periodization. [1] This is a list of such named time periods as defined in various fields of study. These can be divided broadly into prehistoric periods and historical periods (when written records began to be kept). It starts on the first day of your last period and ends on the first day of your next period. Though the average cycle is 28 days long, anything between 21 and 34 days is considered normal.... Your menstrual cycle is the time from the first day of your menstrual period until the first day of your next menstrual period. Every person’s cycle is slightly different, but the process is the same. How long is a normal menstrual cycle? The average length of a menstrual cycle is 28 days.