World clocks
Live local times in major cities. UTC offsets handle daylight saving automatically.
Time-zone converter
Pick two cities and see what time it is in each. Type a time to compare across zones.
Latitude & longitude explorer
Click anywhere on the map to drop a pin and read its coordinates. Lines mark Earth's key parallels and meridians.
Same moment, different places
It's the same instant in all of these cities — only their local clocks differ.
Quick reference
The fundamentals of how Earth keeps time and tells you where you are.
Latitude
Lines of latitude run east-west, parallel to the equator. They measure distance from the equator north or south, in degrees: 0° at the equator, 90° N at the North Pole, 90° S at the South Pole.
One degree of latitude is roughly 111 km (69 miles) — and that distance stays nearly constant from the equator to the poles, because lines of latitude are circles of decreasing size that share the same spacing.
Longitude
Lines of longitude (meridians) run north-south, from pole to pole. They measure how far east or west you are from the prime meridian at 0°, which runs through Greenwich, London. Coordinates run from 0° to 180° east or west.
One degree of longitude is ~111 km at the equator but shrinks as you move toward the poles — at 60° latitude it's only half that, and at the poles, all meridians meet at a single point.
Time zones
Earth rotates 360° in 24 hours, so each 15° of longitude corresponds to roughly one hour of time. Time zones group regions that share a common offset from UTC (Coordinated Universal Time, formerly GMT).
There are about 38 active offsets — not just 24 — because some places use half-hour or quarter-hour offsets (India: UTC+5:30, Nepal: UTC+5:45).
Daylight saving time
Many countries shift clocks forward in spring and back in autumn to better align waking hours with daylight. The shift is usually one hour. About 70 countries observe DST; most equatorial nations don't (their day length barely changes).
The international date line
An imaginary line near 180° longitude. Cross it traveling west — say, from Hawaii to Tokyo — and you advance one calendar day. Cross east, and you go back a day. The line zigzags around political boundaries so each country stays on a single date.
Reading coordinates
Coordinates are usually written as latitude, longitude: e.g. New York City is 40.7° N, 74.0° W. North/South tells the hemisphere from the equator; East/West tells it from the prime meridian.
Decimal degrees are most common in software (e.g. 40.7128, -74.0060). Negative latitude means south; negative longitude means west.
For teachers
Printable worksheet, answer key, teaching tips and standards alignment.
Teaching tips
Standards alignment
Discussion prompts
- Why does the Prime Meridian pass through Greenwich? Why not Paris, Beijing, or Mecca? (Historical-political — international conference, 1884.)
- Why isn't every time zone exactly 1 hour from the next? (India is UTC+5:30; Nepal UTC+5:45; China uses one zone despite spanning ~5 natural zones.)
- If you fly west across the International Date Line, do you gain or lose a day? Why?
- How do longitude and latitude help GPS work? What's the difference between geographic and projected coordinates?
Quick reference
World map
Real OpenStreetMap with all 47 cities and their current local time. Click a pin for details.