Д150
В ОДИН ПРЕКРАСНЫЙ ДЕНЬВ ОДНО ПРЕКРАСНОЕ ВРЕМЯ rather
litPrepPthese forms onlysent
advfixed WO on one particular, significant, or memorable day, on a given day, occasion, at a certain point (often used as a stylistic device to give the flavor or a fairy tale, epic, or the like)
one fine day
(in refer, to the future) one of these days.