21 July - The Temple of Artemis in 356 BC

The Temple of Artemis or Artemision, also known less precisely as the Temple of Diana, was a Greek temple dedicated to an ancient, local form of the goddess Artemis (associated with Diana, a Roman goddess). It was located in Ephesus (near the modern town of Selçuk in present-day Turkey). It was completely rebuilt twice, once after a devastating flood and three hundred years later after an act of arson, and in its final form was one of the Seven Wonders of the Ancient World. By 401 AD it had been ruined or destroyed.Only foundations and fragments of the last temple remain at the site.

The earliest version of the temple (a temenos) antedated the Ionic immigration by many years, and dates to the Bronze Age. Callimachus, in his Hymn to Artemis, attributed it to the Amazons. In the 7th century BC, it was destroyed by a flood. Its reconstruction, in more grandiose form, began around 550 BC, under Chersiphron, the Cretan architect, and his son Metagenes. The project was funded by Croesus of Lydia, and took 10 years to complete. This version of the temple was destroyed in 356 BC by Herostratus in an act of arson.

In Greek and Roman historical tradition, the temple's destruction coincided with the birth of Alexander the Great (around 20/21 July 356 BC). Plutarch remarked that Artemis was too preoccupied with Alexander's delivery to save her burning temple

The next, greatest and last form of the temple, funded by the Ephesians themselves, is described in Antipater of Sidon's list of the world's Seven Wonders.

21 July - The Insat-1C launched in 1988

The Insat-1C satellite was launched on 21 July 1988 from Kourou for location at 93.5°E to bring the Insat system up to full capacity.The INSAT-1C also had a data channel for relaying meteorological, hydrological, and oceanographic data from unattended land-based or ocean-based data collection and transmission platforms.

The designed to provide combined telecommunications, direct TV broadcast, and meteorological service to India's civilian community over a 7-year-in-orbit life span. The telecommunications package provided two-way, long-distance telephone circuits and direct radio and TV broadcasting to the remotest areas of India. 

The INSAT-1C was the third spacecraft in the first generation Indian National Satellite system. 
Half of the 12 C-band transponders and its two S-band transponders were lost when a power system failure knocked out one of the two buses, but the meteorological earth images and its data collection systems were both fully operational. Earth lock was lost 22 November 1989 and the satellite was abandoned. Reported insurance payout was $70 million.

21 July - Neelam Sanjiva Reddy was elected President in 1977

Neelam Sanjiva Reddy (19 May 1913 – 1 June 1996) was the sixth President of India, serving from 1977 to 1982. Beginning a long political career with the Indian National Congress Party in the Indian independence movement, he went on to hold several key offices in independent India—as the first Chief Minister of Andhra Pradesh, a two-time Speaker of the Lok Sabha and a Union Minister—before becoming the youngest-ever Indian president.

Neelam Sanjiva Reddy was elected on 21 July 1977 and was sworn in as the sixth President of India on 25 July 1977. Reddy worked with three governments, with Prime Ministers Morarji Desai, Charan Singh and Indira Gandhi.Reddy announced, on the eve of India's thirtieth anniversary of Independence, that he would be moving out of the Rashtrapati Bhawan to a smaller accommodation and that he would be taking a 70 percent pay cut in solidarity with India's impoverished masses.

21 July - National Junk Food Day

National Junk Food Day comes on July 21 of every year. National Junk Food Day is a day to forget all your diet’s and indulge in all your favorite unhealthy snacks without any guilt. Junk food is a word used to refer the food which has a lot of calories but very little or no nutritional value. Junk Food is popularized in the United States of America from the year 1950, and it is used across the world for foods which are heavily processed and having the high quantity of sugar, salt, and fat.