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A woman can use a calendar to track her menstrual cycle by marking or circling each date of her period on the calendar, starting from the first day of the period, explains GirlsHealth.gov. She can count her full cycle fr... More »

www.reference.com Health Women's Health Menstruation

The modern calendar was created by Pope Gregory XIII in 1582. He introduced the calendar as an adaptation of the Julian version because the drift of Easter, which was tied to the spring equinox, was considered undesirabl... More »

www.reference.com History Inventions

Find an ovulation calendar online, such as the one offered by BabyHopes.com. It calculates and shows the most fertile days of the month based on the menstrual cycle length and the first day of the last period. More »

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A woman's period starts between 21 and 35 days from the first day of her last period, notes the Office on Women's Health. For teens, the cycle may be 21 to 45 days from the first day of their last period. The average men... More »

www.reference.com Health Women's Health Menstruation

Black period blood is usually just a sign that old blood is leaving the uterus toward the end of a woman's menstrual cycle, according to WebMD. It is likely not a cause for concern but can indicate in some cases that a w... More »

www.reference.com Health Women's Health Menstruation

The most common reason for having two periods in one month is when a woman has a short cycle and one period occurs at the beginning of the month, and then about 24 days later, another occurs at the end of the month, acco... More »

www.reference.com Health Women's Health Menstruation

A menstrual period that only lasts a single day is not normal or common, but every woman's cycle is different, explains Mayo Clinic. Women should closely monitor their start date, end date, flow and pain levels each mont... More »

www.reference.com Health Women's Health Menstruation