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.

20 July - Alexander the Great birth anniversary

Alexander III of Macedon ( 20/21 July 356 BC – 10/11 June 323 BC), commonly known as Alexander the Great (Aléxandros ho Mégas), was a king (basileus) of the ancient Greek kingdom of Macedon[a] and a member of the Argead dynasty. He was born in Pella in 356 BC and succeeded his father Philip II to the throne at the age of 20. He spent most of his ruling years on an unprecedented military campaign through western Asia and northeast Africa, and by the age of thirty, he had created one of the largest empires of the ancient world, stretching from Greece to northwestern India.He was undefeated in battle and is widely considered one of history's most successful military commanders.

Alexander was born in Pella, the capital of the Kingdom of Macedon,on the sixth day of the ancient Greek month of Hekatombaion, which probably corresponds to 20 July 356 BC, although the exact date is uncertain.He was the son of the king of Macedon, Philip II, and his fourth wife, Olympias, the daughter of Neoptolemus I, king of Epirus.Although Philip had seven or eight wives, Olympias was his principal wife for some time, likely because she gave birth to Alexander.

20 July - Lempira Day

Lempira Day is a Honduran holiday celebrated annually on July 20. It is dedicated to an indigenous leader of the Lenca people who led the resistance against the Spanish conquistadors in the 1530s.

In 1533, Spanish conquistador Francisco de Montejo received a royal decree that gave him permission to conquer certain parts of Honduras. He then attempted to conquer the territory inhabited by the Lencas in western Honduras.

Chief Lempira organized resistance against the Spanish conquerors and gathered an army of about 30,000 people. Unfortunately, the resistance was ultimately unsuccessful. The Spaniards lured Lempira out to talk and then shot him dead. After their leader’s death, the Lenca surrendered.

Despite the defeat of Lempira's uprising and the subsequent conquest of Honduras, the Lenca leader is considered a national hero of Honduras. The currency of Honduras and one of the country’s 18 departments were named after him. Besides, Lempira is portrayed on the 1 lempira note.

Although Lempira Day is not a public holiday, it is widely celebrated throughout in Honduras, especially in schools (most Honduran schools are in session in July). On this day, children dress up as indigenous Hondurans and prepare presentations of different ethnic groups. Lempira Day is more than a holiday dedicated to a national hero, it is a celebration of indigenous culture and heritage.

Source : https://anydayguide.com/

20 July - Viking 1 Lander lands on Mars in 1976

Viking 1 was the first of two spacecraft (along with Viking 2) sent to Mars as part of NASA's Viking program.On July 20, 1976, it became the second spacecraft to soft-land on Mars, and the first to successfully perform its mission. (The first spacecraft to soft-land on Mars was the Soviet Union's Mars 3 on December 2, 1971, which stopped transmitting after 14.5 seconds.) Viking 1 held the record for the longest Mars surface mission of 2307 days (over 6​1⁄4 years)or 2245 Martian solar days,until that record was broken by the Opportunity rover on May 19, 2010.

20 July - Geeta Dutt death anniversary

Geeta Dutt (born Geeta Ghosh Roy Chowdhuri; 23 November 1930 – 20 July 1972) was a prominent Indian playback singer and a famous Hindi and Bengali classical artist, born in Faridpur before the Partition of India. She found particular prominence as a playback singer in Hindi cinema. She also sang many modern Bengali songs, both in the film and non-film genre.

Geeta Dutt died on 20 July 1972 due to cirrhosis of liver at the age of 41 in Mumbai, Maharashtra. She was survived by her three children and siblings.

20 July - Haakon, Crown Prince of Norway born in July 1973

Haakon, Crown Prince of Norway (Haakon Magnus; born 20 July 1973) is the only son of King Harald V and Queen Sonja, and heir apparent to the throne of Norway.

In 2001, Haakon married Mette-Marit Tjessem Høiby with whom he has two children. He has an older sister, Princess Märtha Louise. In accordance with Norway's agnatic primogeniture succession, Haakon became crown prince when his father ascended the throne on 17 January 1991 upon the death of his grandfather Olav V.

The Skaugum Estate, situated in the area of Semsvannet, is the official residence of the Crown Prince and Crown Princess

20 July - Krishna Kanta Handique birth anniversary

Krishna Kanta Handique (20 July 1898 – 7 June 1982) was a Sanskrit scholar, an Indologist and philanthropist from Assam. He was a recipient of the civilian honour of the Padma Shri and Padma Bhushan

The Indian Posts and Telegraphs Dept. issued a commemorative stamp in honor of Prof. Handique on 7 October 1983. The Govt of Assam has instituted the prestigious Krishna Kanta Handique Memorial Award in his honour in the field of promotion of Sanskrit language and literature.

Handique, the Sanskrit scholar is known for his three major works:

Naisadhacarita of Sriharsa, 1934
Yasastilika and Indian Culture 1949
Pravarasena's Setubandha 1976