My oldest one at 2 and half months, my youngest at 3 and a half months.
I started off with a combo of breastfeeding and formula for the first 1-2 months, then switched to formula only after that because I was having trouble with breastfeeding. In both cases, when they started sleeping through the night it was from about 9:30 or 10:00pm until about 6:30am. After about 4-5 months old they settled into a longer sleeping routine of about 8:00pm until 7:00am.
They had very different 'sleep personalities' though, my older would only wake to feed and then go straight back to sleep, the younger needed more soothing and holding after each feed to get him back to sleep. In both cases I always did diaper change right before feeding at each night-time wake-up, it meant that after the feed I could just put them back to bed or cuddle and soothe them without needing to get them all 'active' again for a diaper change.