How does Calgary and London have different climates even being located from the same latitude on Earth?

Calgary (North America) and London (Europe) have different climates even being located from the same latitude on Earth is due to the gulf stream (warm, fast ocean current).

Explanation:

The location of a place in the north or south of the equator is provided by latitudes. The higher latitudes (away from the equator) receive less heat than lower latitude areas nearer the equator because different latitudes receive different amounts of sunlight. Climate of the earth depends on the latitude, the arrangement of oceans and land masses, and ocean currents.

The places near to oceans, like London is warmer in winter and cooler in the summer. The light from the sun warms up the ocean and some of this heat is transferred to the air making the land warmer. Also the oceans move heat around the earth as the water in the ocean is always moving. This moving of ocean water is known as ocean current.

The Gulf Stream is a strong, fast and warm ocean current, which is caused by the clockwise flow of water in the North Atlantic, that draws warm water from the equatorial region (Gulf of Mexico). The winds from the Arctic causes the cooling of surface water in the North Atlantic ocean. Some of the water evaporates making the rest more salty and dense, and as a result the cold water sinks into the ocean floor. Then it moves towards the equator and gets warm slowly. The warm water from the Gulf of Mexico then moves into the Atlantic (Gulf Stream) to replace the cold equator-bound water.

This warm ocean current and the warmer airflow associated with it increases the temperatures of the most of Europe while North America has ocean currents that originate in the colder regions and bring colder weather onto land.