what is considered the first day of your last period?
Your cycle begins on the first day you have regular bleeding. Spotting doesn't count. For example, Cycle Day 1 is the first day of your period; Cycle Day 2 is the second day of your period, Cycle Day 3 is the third day of your menstrual flow, and so forth. ... The first day of your period is also called “Cycle Day 1”.