UPSC Prelims 2025 Q77: International Date Line, Anadyr & Nome
Consider the following statements:
I. Anadyr in Siberia and Nome in Alaska are a few kilometers from each other, but when people are waking up and getting set for breakfast in these cities, it would be different days.
II. When it is Monday in Anadyr, it is Tuesday in Nome.
Which of the statements given above is/are correct?
- I only
- II only
- Both I and II
- Neither I nor II
Answer: (a) I only
Statement-wise explanation
- I: correct — Anadyr is the capital of Chukotka in Russia. It keeps UTC+12 all year. Nome in western Alaska keeps UTC−9 in winter and UTC−8 in summer. So Anadyr is 20–21 hours ahead, and the International Date Line runs between the two towns through the Bering Strait. At 7 a.m. Tuesday in Anadyr it is 10–11 a.m. Monday in Nome, so breakfast in the two towns falls on different calendar days. One caveat: the towns are about 800 km apart, not 'a few kilometres'. The pair that really is a few kilometres apart is the Diomede Islands, about 4 km apart. The statement's point about the date is still right.
- II: incorrect — The statement gets the direction wrong. Anadyr lies west of the Date Line, so it is ahead in time. When it is Monday in Anadyr, it is Sunday in Nome for most of the day. For the last 3–4 hours of Monday night in Anadyr it is early Monday in Nome. It is never Tuesday in Nome while it is still Monday in Anadyr. Crossing the Date Line westward adds a day; crossing it eastward takes a day away.
How to eliminate
You need one rule: the Asian side of the Date Line is a day ahead of the American side. Anadyr is in Asia (Russia) and Nome is in America (Alaska), so Anadyr is always ahead. That alone rules out Statement II, which puts Nome ahead. That leaves 'I only' or 'Neither'. Statement I says only that the two towns are on different days at breakfast. With a gap of about 21 hours this is almost bound to be true, because each town's morning falls on the other's previous or next date. The loose wording 'a few kilometres' (the real distance is about 800 km) may push some candidates toward 'Neither'. UPSC was testing the date, not the distance. Remember: west of the line = later date (Russia, Kiribati, New Zealand); east of the line = earlier date (Alaska, Hawaii, Samoa's neighbour American Samoa).
Know more
International Date Line (IDL)
The Earth turns 360° in 24 hours, so each 15° of longitude equals one hour. Go east from Greenwich and local time runs ahead. At 180°E a place is 12 hours ahead. Go west and time runs behind, reaching 12 hours behind at 180°W. Both are the same meridian, so places on either side of it are a full 24 hours (one calendar day) apart. The IDL is where that one-day jump happens.
- It roughly follows the 180° meridian in the mid-Pacific, which was chosen because it crosses almost no land.
- It zigzags so that no country is split across two dates. It bends east through the Bering Strait to keep all of Siberia on the Asian date. It bends west to keep the Aleutian Islands with Alaska. In the south it bends east around Kiribati, Fiji, Tonga and Samoa.
- It has no legal international status. Each country chooses its own date. Samoa moved to the west side in 2011, and Kiribati moved its eastern islands in 1995.
- Crossing rule: going west, add a day. Going east, subtract a day.
| Pair across the IDL | West side (ahead) | East side (behind) |
|---|---|---|
| Bering Strait towns | Anadyr, Russia (UTC+12) | Nome, USA (UTC−9) |
| Diomede Islands (~4 km apart) | Big Diomede, Russia | Little Diomede, USA |
| South Pacific | New Zealand (UTC+12) | Hawaii (UTC−10) |
Because time zones follow national borders, some places run more than 12 hours ahead of UTC. Kiribati's Line Islands keep UTC+14, the earliest time zone on Earth.
NCERT Concepts to Revise
- International Date Line: Both statements depend on which side of the Date Line is a day ahead of the other.
- Bering Strait: Anadyr and Nome face each other across the Bering Strait, which is where the Date Line separates Russia from Alaska.
- Longitude and time: The hour gap between Chukotka and western Alaska comes from the rule linking longitude to time.
- Local time: Breakfast time in each town is its local clock time, which you need when comparing the two calendar dates.
- Kiribati date line shift: Kiribati's shift shows that countries choose their own side of the Date Line, as Russia and the USA do in the Bering Strait.