In mammals, the period during a female's reproductive cycle (also known as the oestrus cycle or menstrual cycle) when mating is most likely to occur. It usually coincides with ovulation, when egg cells are released from the ovary.
Red and white are the colours of Bohemia, dating back to the 13th century. Blue represents Moravia. Unlike that of the Slovak Republic, the Czech flag is not based on the pan-Slav colours. Effective date: 1 January 1993.