Standard meridians are lines of longitude based off the Greenwich Prime Meridian that are divisible by 15. They are used for determining the standard time zones of a location. There are 24 standard meridians across the globe. The distance between standard meridians is 111 kilometers at the equator. As they approach the poles, the distance between meridians decreases.

Russia contains more contiguous standard meridians than any other country. This is not surprising, as the distance between its eastern and western borders is about 9,000 kilometers, making it the longest country. Being in far northern latitudes also means that the distance between meridians is less than if the country were closer to the tropics. Eleven standard meridians pass through Russia. These are 30, 45, 60, 75, 90, 105, 120, 135, 150, 165, and 180 degrees. Consequently, Russia has eleven time zones.

The country of Brazil has two standard meridians. These are -45 and -60 degrees. Even though the country is over 4,000 kilometers from East to West, its tropical location means that the distance between its standard meridians is relatively great.

France has just one standard meridian: 0 degrees, the Prime Meridian.

South Africa is bisected by the standard meridian of 30 degrees.

Australia has three standard meridians. These are 120, 135, and 150 degrees.

Unlike latitude which is defined by the rotation of the Earth, longitude is arbitrarily defined; we could have put the prime meridian wherever we wanted, and actually until an international conference standardized it at Greenwich different countries put it in different places.

The standard meridians are those which are at 15-degree offsets from that Greenwich prime meridian, and they are roughly aligned with the time zones because 360/15 = 24.

Russia has a whole bunch of them; all the meridians from 30 to 180 all pass through Russia, so its standard meridians are 30, 45, 60, 75, 90, 105, 120, 135, 150, 165, 180.

Brazil contains standard meridians -45 and -60.

France contains only the 0 standard meridian, the same one as Greenwich.

South Africa contains the 30 standard meridian.

Finally, Australia contains 120, 135, and 150.