There is no such longitude. The maximum degrees for lines of longitude is 180 east and west only.
Zulu Time = UTC
There are 15 degrees of longitude in each standard time zone
360° of longitude divided by 24 time zones gives 15° per time zone (average)
No line of longitude bends, but the time-zone boundaries are defined to depart from the meridians in order to accomplish that.
The central meridian for the irregular time zone that includes India is 82.5 degrees east. India Standard Time (IST) is determined based on this central meridian.
latitude and longitude
It is a time zone.
earths rotation
The time zone centered at 120° west longitude is UTC-8.
That would be zero degrees longitude.
earths rotation
There are 24 time zones. Divide 360 degrees longitude by 24 and you get 15 degrees for each one-hour time zone.