Two definitions straight from the Oxfordcitionaries
pastime (n) – An activity that someone does regularly for enjoyment rather than work; a hobby.
timepass (n) – The action or fact of passing the time, typically in an aimless or unproductive way.
The latter word is Indian English. Though the dictionary has not mentioned this word as a verb, here, it's common to say (though in an informal way) "Don't timepass, the work has to be finished in an hour."
What if I want to refer pastime as timepass and timepass as pastime. In other words, what if I want to ask a native speaker that how does s/he passes her time (timepass) and an Indian about how does s/he does pastime?
An example for the native speakers on timepass:
"Narendra, why are you throwing stones in the river?" ~ "Ah, I'm waiting for my friend. She hasn't come yet."
"And throwing stones?" ~ "Just simply… timepass."
Here, by no means timepass is done for enjoyment. Nor is it a hobby.
Note: To most of Indians, pastime is actually timepass. Because if you ask about pastime, you are very likely to get an answer about timepass.
Best Answer
Only users of Indian English can tell you how to express the 'Standard English' sense of pastime in Indian English; and to all appearances you are our authority on Indian English dialects.
I might remark, however, that pastime is literary or academic and is not often encountered in colloquial registers. "What do you do as a pastime?* is far more likely to be
For a Standard English equivalent of InE timepass in the contexts you present, I suggest waste time for the first and kill time or pass the time for the second.