Baby sleeping at 3-4am

TL;DR: MY BABY SLEEPS AT 4AM, WAKES AT 4PM *HELP* Hi mommies! My 5month baby sleeps for 9-12 hours stretch with max 2 night feedings (mostly 1 feed, and if we feed her more during her last feed, she can actually go without a night feed) at the moment - but she would only do it after 3am. We do get a good 8 hour sleep minimally which is good since we dont wake up early anyway but it's quite impossible to keep up with this schedule as we are back at work / she's living with my inlaws on weekdays. This actually happened after her 4th month regression (she used to sleep 1130pm - 1030am before it happened) could this be the cause of it? She rejected sleep then and would only take very short naps for 2 weeks straight, with very frequent feedings. Any suggestions on how I can shift her sleep timing earlier would be appreciated! FYI: She has 3 naps a day (30mins to 1.5hrs), with 1.5-2hrs awake time (activity) each time (quite consistent) which we think is quite healthy? 4 to 6 mixed feeds (we try to give her formula for her last feed so she will be 'full') her total sleep hours add up to the recommended hours too... Current sleep pattern: 2pm wake + activity - 4pm nap - 5pm activity - 7pm nap - 8pm wake - 10pm nap - awake till 2am 😴 (if she sleeps at 4am, she can sleep till 4pm lol) Is 7pm considered her bedtime even if it's not a long stretch? My inlaws have to entertain her till 2am and it's quite unhealthy for older folks 🤣 Tried: - Nursing her to sleep but it only worked once. Her eyes will be wide open after unlatching and she will start babbling (active with that feed and short nap) - Keeping the room dark - Letting her cry for a bit but usually it will turn murderous lol (my poor neighbours)