Time Zones

Convert time between cities with daylight saving time, find local solar time by longitude (15° = 1 hour) and the time zone number.

What to find:

the time in another city

local solar time by longitude (15° = 1 hour)

the time zone number by longitude

Time as h:mm. Coordinates in degrees: 55.75, 55°45′, 55 45 21, 55°45′ N; southern latitude and western longitude with a minus sign or the letters S / W.

Test yourself

The time zone calculator converts the time from one city to another using the current time zones and daylight saving time, finds local solar time from the difference in longitude and determines the time zone number from the longitude.

Local time and longitude

The Earth makes a full turn (360°) in 24 hours, turning 15° per hour and 1° per 4 minutes. So at a place further east the local time is later, and further west it is earlier:

Δt = Δλ · 4 min, 15° = 1 h

Standard time zones

The Earth's surface is divided into 24 time zones 15° wide. The zone number is the longitude divided by 15° and rounded; the central meridian of zone 0 is the Greenwich meridian. Within a zone the time is the same. Real time zone borders follow the borders of countries and regions, so official time may differ from the nautical zone time.

Example 1. It is 12:00 in Moscow (UTC+3). In Vladivostok (UTC+10) it is 12:00 + 7 h = 19:00.

Example 2. It is noon at 30° E. At 60° E the local time is later by 30 · 4 = 120 min: 14:00.