Time zones
Why India is UTC+5:30 and Nepal is UTC+5:45
India and Nepal show why whole-hour offsets are not a rule. Their national clocks are fifteen minutes apart, despite sharing a long border and broadly similar longitude.
A national half-hour clock
India uses Indian Standard Time, UTC+5:30. It is one nationwide civil clock, rather than a stack of whole-hour bands. The extra half hour is a deliberate public standard; it is not a technical rounding error or a temporary daylight-saving setting.
Nepal adds another quarter hour
Nepal Standard Time is UTC+5:45, placing it fifteen minutes ahead of India. Nepal’s aviation and government material uses the same quarter-hour offset. The two countries make a useful everyday demonstration that the decimal-looking offset is still an exact civil-time rule.
The scheduling lesson
A call at 09:00 in Delhi is 09:15 in Kathmandu. Software that assumes every zone is an integer number of hours will be wrong. Store Asia/Kolkata or Asia/Kathmandu with an event, and display the calculated result for the date in question.