An interactive cultural timeline

4th July : Independence Day (USA)

The Fourth of July is the national celebration of the Independance of the United States of North America.

4th July : Independence Day (USA)

Fourth of July parade. Photo Luc Byhet (CC BY-NC-SA).
Fourth of July at the Capitol, Washington DC. Photo Joe Newman (CC BY-NC-SA).

The Fourth of July, or Independance day is a federal holiday in the USA. It recalls the beginning of the revolt of the American colonists against the authority of the King of Great Britain. The Declaration of Independance from Great Britain was signed by elected delegates meeting in Congress on July 4th, 1776.
12th July : Orange Men's Day (Northern Ireland)

The Glorious Twelfth proclaims the fidelity of Protestant Ulstermen to the United Kingdom.

12th July : Orange Men's Day (Northern Ireland)

Orange March Belfast. Photo Micah McAllen (CC BY-NC-SA).

This day is known as "Orangemen's Day, Orange Day, the Glorious Twelfth or just the Twelfth. In 1690, Protestant king William III of England defeated the exiled Catholic king James II Stuart at the Battle of the Boyne, on Ireland’s east coast. James had been a refugee in France at Louis XIV’s court in Versailles, he had invaded Ireland with French troops and was preparing to reconquer England from there.

Protestant Irishmen march with drums and pipes, they wear orange sashes, black suits and bowler hats. Orange was the colour of Dutch prince Willem van Oranje who became King of England. Orange Day marches also take place in Birmingham and Liverpool, and in some parts of Canada where Irish Protestants emigrated.
16th - 20th July : Swan Upping

A curious and colourful tradition of the Upper Thames region in England.

16th - 20th July : Swan Upping

Swan upping rowboat. Photo David Quick (CC BY-NC-ND).

A census of swans takes place annually during July on the River Thames, in a ceremonial boat trip known as Swan Upping. Swans living alogside the river are counted and marked on a 70 mile, five day journey up the River Thames. The Swan Upping event commences on the third Monday at Sunbury and ends at Abingdon on the Friday.
17th July : Yellow Pig Day

Yellow Pig Day is a mathematician's holiday celebrating yellow pigs (and why not ?), together with the number 17.

17th July : Yellow Pig Day

A few members of David Kelly's yellow pig collection. Photo Maksim (Public domain).
Yellow pig. Photo Anita Hart (CC BY-SA).

The Yellow Pig was the brainstorm of mathematicians Michael Spivak and David C. Kelly at Princeton University in the early 1960s. They were listing interesting properties of the number 17. During this thought wave, the yellow pig was born. Obviously it has 17 toes, 17 teeth, 17 eyelashes, etc. Mathematicians have a queer sense of humour, remember Lewis Carroll who wrote Alice in Wonderland was also a mathematician. The yellow pig and the number 17 have been linked ever since.

It is celebrated annually on the 17th of July since then, primarily on college campuses, and primarily by mathematicians. On campus, you may eat Yellow Pig Cake (yumyum) and sing Yellow Pig Carols (about numbers and pigs). If you are a mathematician, you may spend the day thinking and working in multiples of 17. Thinking of yellow pigs naturally.