Day-night confusion
Also called day/night confusion, day and night confusion, days and nights mixed up, day and night mixed up, days and nights confused
Day-night confusion is when a newborn sleeps long stretches in the day and wakes much more at night, as if day and night were swapped. Parents also say a baby has their days and nights mixed up.
How it's said
She's sleeping pretty well (much better than I expected) but does seem a bit confused about day and night.
Babies do get day and night confused to start with but they do grow out of it.
Don't worry, you're not alone; many babies (and parents!) struggle with day-night confusion.
Who says it
Where it came from
The phrase describes a newborn whose body clock hasn't set yet. Pathways.org explains that babies aren't born with a circadian rhythm, the internal clock that tells the body when to sleep and when to wake.
Sleep consultants write it as day/night confusion as often as day-night confusion, and describe it as common in the first three months.