it depends what you mean by routine, and from new born , or not, and routine for feeding or for nap times.....
i let my babies find their own routines, and followed their lead as much as i could
.. i know one couple who tried to follow a routine from a well known baby book,... and got terribly frustrated when their baby didn;t fit the routine.....
i got to know my babies, what cry meant hungry, what meant tired, or bored ,or windy.. DS definitely had no routine to speak of, until he went to nursery.... DD had to fit into the pattern of the school run but i didn;t follow a written set of rules or a routine from a book or a guru
so ,most people i know did not follow a regime from a book or of their own, but as your baby gets older, you often find they tend to want to feed and sleep at similar times....