The simplest answer is 180 degrees.
However, it bends and weaves quite a lot by convention to avoid some islands.
In fact some islands are east of the line and have a negative time zone and some are west of the line and have a positive time zone.
Las Vegas is approximately 116 degrees west of the International Date Line, which lies at 180 degrees longitude. Therefore, there are about 64 degrees of longitude separating Las Vegas from the International Date Line.
The International Date Line is an imaginary line located at about 180 degrees longitude, mostly in the Pacific Ocean. It separates one calendar day from another when moving east or west across it.
The international date line
The major line of longitude located at 180 degrees longitude is the International Date Line.
This line is known as the antimeridian or simply the 180th meridian. The international date line is sometimes used although it is not entirely correct. The international date line is a "political" convention and sometimes deviates signifigantly from the actual 180 degree longitude
The International Dateline approximately follows the meridian of 180° longitude.
The International Dateline approximately follows the meridian of 180° longitude.
Whether travelling to the West or to the East from the Prime Meridian (zero Longitude) the International Date Line is 180 degrees Longitude.
121 degrees east longitude
Las Vegas is approximately 116 degrees west of the International Date Line, which lies at 180 degrees longitude. Therefore, there are about 64 degrees of longitude separating Las Vegas from the International Date Line.
International Date Line
The international date line (or there abouts)
No. 90 degrees longitude is not a major line of longitude. Only 0 and 180 degrees longitude, which are the Greenwich Meridian and the International Date Line respectively, are major lines of longitude.
The International Date Line is an imaginary line located at about 180 degrees longitude, mostly in the Pacific Ocean. It separates one calendar day from another when moving east or west across it.
180 degrees east/west longitude
The international date line
180 degrees