Question

Why does a boring day seem to drag on, while if we are enjoying ourselves,time will seem to fly?

Answer 1

when we are generally busy we lose track of time, while bored we notice it , and feel like it drags.
while enjoying we are pre occupied with something other than time passing or the clock ticking

Answer 2

how a person perceives time is highly subjective and usually depends on the situation.

As per my POV
We all know that practically the speed of time is constant. But when we are enjoying a moment, time seems to fly by way too fastly. This is because while enjoying, we usually forget about time and when the moment has ended, we are like 'whoa! This early?'
And when we are going through a bad phase, we keep the track of time waiting for it to end. When the time has ended we r like, 'whoo! Finally. It took so long.' We get tired of waiting for bad time to end.

But again, it's just the person's perspective.