how many days off for period
A normal menstrual cycle lasts 28 days, plus or minus seven days. Menstrual bleeding is considered irregular if it occurs more frequently than every 21 days or lasts longer than 8 days. Missed, early, or late periods are also considered signs of an irregular cycle. To determine whether your menstruation schedule is irregular, count from the last day of your previous period and stop counting on the first day of your next. Repeat this for three months.