Yes, there is a reason why females crave chocolate.

Acute monthly cravings for chocolate amongst pre-menstrual women could be explained by chocolates rich magnesium content. Magnesium deficiency exacerbates pre-menstral tension. Before menstruation the hormone levels of progesterone are high. Progesterone promotes fat storage, preventing its use as fuel; elevated pre-menstrual levels of progesterone may cause a periodic craving for fatty foods. One study even reported that 91% of chocolate-cravings associated with the menstrual cycle occurred between ovulation and the start of menstruation. Chocolate cravings are admitted by 15% of men and around 40% of women.

Fyi- Cravings are usually most intense in the late afternoon and early evening.