There are four important parallels of latitudes on the Earth. They are:
(i) Tropic of Cancer It is an imaginary line that crosses at 23 1 / 2° in Northern hemisphere.
(ii) Tropic of Capricorn It is an imaginary line that crosses at 23 1 / 2° in Southern hemisphere.
(iii) Arctic Circle It is a circle at 66 1 / 2° North of the equator.
(iv) Antarctic Circle It is a circle at 66 1 / 2° South of the equator.

The value of each latitude is followed by the letter 'N' or'S'. The parallel of latitudes in the North of the equator is represented as 'N' while the parallel of latitudes in South of the equator is represented as'S'.

The local time of places on different meridians are bound to differ. The time difference within a country may be more than two hours. Therefore, it is necessary to have a standard time for a country. That's why the Earth is divided into 24 time zones.

Parallels of latitudes: All parallel circles from the equator upto the poles are called parallels of latitudes. This is an imaginary line and measured in degree.
Meridians of longitudes: All of the imaginary lines running from the North Pole to South Pole. The distance between them is measured in degrees.

A globe is a true model of the earth. It shows the earth in its real shape with continents, oceans and
tilt on its axis.

(i) 23°30' N is value of the Tropic of Cancer.
(ii) Frigid zone is situated between 66030' and poles.

Local time is based on the local meridian passing through that place. The places lying North and South on the same meridian will have the same local time and the places lying East or West of that meridian will have different local times. It is important because the time for any country is measured by the local time. The local time of places on different meridians are different. Therefore, it will be difficult to prepare time-table for trains which cross several longitudes.
For example There will be a difference of about 1 hour and 45 minutes in the local times of Dwarka in Gujarat and Dibrugarh in Assam. Therefore, it is necessary to adopt the local time of some central meridian of a country as the standard time for the country.