Infant colic mostly occurs between 2-4 weeks after birth, generally reaching a peak around one and a half months after birth. The symptoms of infant colic primarily include four aspects: firstly, the child will suddenly start crying loudly and inconsolably, which is clearly different from usual. Second, the crying episodes can last particularly long, even up to about three hours, and may occur more than three times a week. Thirdly, these episodes generally occur in the evening or late at night, hence the colloquial term "twilight crying." Fourthly, with colicky infants, conventional soothing methods are ineffective; for example, holding or comforting the baby does not help, and the child continues crying until completely exhausted before falling asleep. This is a typical symptom of infant colic.