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.
Count the first day of your period as day one. Your fertile window is likely to be around days 12 to 17. However, a lot of women have an irregular cycle. If your cycle is irregular, ovulation may occur a week earlier or later from one month to the next (Fehring et al 2006) .