I have come across this weirdly formed phrase in a book , but i am not sure of its correctness. If this is correct, what would be its proper usage?
Is saying "I met you a long time later" correct?
At first glance, there seems to be nothing wrong with that sentence. A long time is just another period of time, like a week or a year, and it can be substituted for those:
I have been working here for a week.
I have been working here for a year.
I have been working here for a long time.
So it makes perfect sense to use it in a similar way in a sentence like:
I met him a week later.
I met him a year later.
I met him a long time later.
However, it somehow feels “off”. I suspect this may have to do with the fact that we can convey the exact same meaning in a more concise way:
I met him much later.
Indeed, if we look at Google nGrams, we see that both a week later and a year later are commonly used, but a long time later, though it is used, is very rare. Much later, however, is used as often as a year later.
So, in conclusion, the phrase is correct, and it is used (if rarely), but the more common, more idiomatic expression would be much later.
We could think of a context like this. In the American drama "Heros", the Japanese guy has an ability to time-travel. So he goes to the future and meets another character that he have not met yet in the present. Then the Japanese comes back to the present and comes across the guy he met in the future, so the Japanese says to him "I met you a long time later"
"a long time later" describes a passage of time between 2 events. A common usage would be in a narrative to link to scenes, the second of which happens "a long time" after the first.
Your usage is incorrect because the tenses are confused "I met" refers to an event in the past, "a long time later" refers to an event in the future - they can't be the same event. Also, it is awkward telling someone that you haven't met that you will have met them.
Something like "A long time later, I will meet you" would be better but still sounds a little strange to me.
What exactly are you trying to say?