The offenders
| Zone | Offset | Population affected |
|---|---|---|
| India | UTC+5:30 | ~1.4 billion — by far the biggest |
| Sri Lanka | UTC+5:30 | ~22 million |
| Myanmar | UTC+6:30 | ~54 million |
| Iran | UTC+3:30 | ~89 million |
| Afghanistan | UTC+4:30 | ~41 million |
| Newfoundland (Canada) | UTC-3:30 | ~0.5 million (observes DST too) |
| Central Australia (Adelaide, Darwin) | UTC+9:30 | ~2 million |
| Nepal | UTC+5:45 | Quarter-hour! ~30 million |
| Chatham Islands (NZ) | UTC+12:45 | ~600 people, still real |
| Eucla (Australia) | UTC+8:45 | Unofficial but locally used |
Why these exist
Time zones are political, not geometric. India spans what would "naturally" be two hours of solar time; rather than split the country, it compromised in the middle — +5:30. Nepal picked +5:45 to set its clocks by a local mountain meridian (and, practically, to be distinct from India). Iran and Afghanistan sit similarly between natural zones. Newfoundland simply kept the solar time of St. John's when zones were standardized. None of this is going away — India has used +5:30 since 1947 and has no plans to change.
Where they bite you
- Mental math rounds to hours. "New York is about 10 hours behind Mumbai" — no, it's 9:30 or 10:30 depending on DST. Round it and you're half an hour off, in whichever direction embarrasses you most.
- Hour-granularity tools round too. Any world clock or scheduling slider that steps in whole hours simply cannot land on "9:00 in Mumbai". The correct answer to "what's 9:00 Mumbai for me?" is always on the half hour for whole-hour zones.
- DST makes it worse. Newfoundland is UTC-3:30 in winter and UTC-2:30 in summer. Half-hour offset and a moving target.
- "IST" is a trap. It means India (+5:30), Israel (+2), and Ireland (+1). Say the city, not the abbreviation — see UTC vs GMT for the full ambiguity problem.
How to schedule with half-hour zones
- Think in 15-minute steps. If anyone on the call is in India, Nepal, or Newfoundland, propose times on the quarter hour. 9:00 Berlin = 12:30 Mumbai = 12:45 Kathmandu.
- Anchor on their time. "Would 10:30 your time work?" eliminates the rounding error at the source.
- Use a tool that doesn't round. This is exactly why GlobalTimeZones' planning slider moves in 15-minute steps rather than hours — drag it and Mumbai lands on :30, Kathmandu on :45, precisely. Try it with the demo — one of the sample cities is on a half-hour offset for exactly this reason.
The takeaway
Nearly two billion people live on offsets that aren't whole hours. If you work with India — and statistically, you will — build the half-hour into your habits and your tools, and "sorry, I had 12:00 not 12:30" disappears from your vocabulary.