my son slept through the night in first 40 days but now since 3 days he is awake the whole night and sleeps through the day .. why sudden change in sleep pattern??

A. Every 15 to 20 days the sleep pattern of the child changes and now previously a child was sleeping through the night now the child will sleep through the day for a while and again the pattern is going to change it is common to be seen for initial 60 days approximately 180 days and maybe sometimes a little more