The carat (ct) is a unit of mass equal to 200 mg (0.2 g; 0.007055 oz) and is used for measuring gemstones and pearls. The current definition, sometimes known as the metric carat, was adopted in 1907 at the Fourth General Conference on Weights and Measures, and soon afterwards in many countries around the world.
Depending on your cycle length the most fertile days in the cycle varies: If you have 28 days between periods ovulation typically happens on day 14, and the most fertile days are days 12, 13, and 14. If you have longer cycles, say 35 days between periods, ovulation happens on day 21 and the most fertile days are days 19, 20, and 21.
The menstrual cycle is the time from the first day of your period to the first day of your next period; for most women, that is about 28 days. About 12-14 days before your period begins, you are most fertile. This is when you ovulate, or release an egg. This is when you are most likely to become pregnant.