Measured time is a relative construct. Whilst a clock my say 5 p.m. in Chicago, a clock in New York reads 6 p.m. and a clock in London is showing 11 p.m. Yet, these are all occurring at the same time.
We can be constrained to act or restrained not to act at certain moments of measured time, e.g., a shop is open for business from 10 a.m. to 5 p.m. or street parking is prohibited from 2 a.m. to 5 a.m. So too the Church can oblige us under measured time, e.g., Mass must be offered between midnight and noon or one must fast from midnight in preparation for Communion.
However, regarding prayers as you enquire, some measured times are merely customary, such as, the times for recitation of the Angelus. Other prayers at other measured times are wholly voluntary.
So, in light of these points, pray when you are able, trying to observe customary times but realising that rarely do these oblige. In short, pray always, pray well.