The longest day of 2017, for anyone living north of the Equator like us in India is 21st June. It occurs when the sun is directly over the Tropic of Cancer, or more specifically right over 23.5 degrees north latitude. This has occurred in Hyderabad today at 09:54 IST, as detailed in the news clipping below:
Since Earth rotates on its axis, the Northern Hemisphere gets more direct sunlight between March and September over the course of a day, which also means people living in the Northern Hemisphere also experience summer during this time. It is during the rest of the year that the Southern Hemisphere gets more sunlight.
The maximum amount of sunlight received by the Northern Hemisphere during this time is usually on 20th, 21st or 22nd June. That is called the summer solstice. In contrast, the Southern Hemisphere receives most sunlight on 21st, 22nd or 23rd December when northern hemisphere has its longest nights– or the winter solstice.
The amount of light received by a specific area in the Northern Hemisphere during the summer solstice depends on the latitudinal location of the place. The further north one moves from the equator, one receives more light during the summer solstice. The northern most countries like Norway, Sweden and Iceland will have daylight for around 20 hours! And at the Arctic Circle, the sun never sets during the summer solstice!
To better understand the summer solstice and its significance and celebration you may see this video: