The difference between night and day may be reinforced in young babies by offering a 'focal feed' between 10pm and midnight and gradually lengthening the intervals between night-time feeds by a variety of other activities (such as nappy changing, re-swaddling and walking with the infant).
Renfrew, M. J., Lang, S., Martin, L., & Woolridge, M. (2000). Interventions for influencing sleep patterns in exclusively breastfed infants. Cochrane Database of Systematic Reviews, (2), [CD000113]. https://doi.org/10.1002/14651858.CD000113