Nepal is 5 hours 45 minutes ahead (+5:45) of GMT (Greenwich Mean Time). Nepal, India, and Sri Lanka all lie in nearly the same longitudinal line. But still, Nepal's time is 15 minutes different from India, whereas Sri Lanka's doesn't.
Mt Gaurishanker is Nepali timeline standard, it is situated in Dolakha Districts. While traveling in Nepal through India, you need to fix your watch to Nepali Time. Sometimes you might be confused.