St George's Day

St George's Day is the national Day of  England, and is held on 23rd April.
If it is St George's Day today so on your travels, you're fairly likely to see some form of a white flag with a red cross on it.  The England flag design can be traced back to the Middle Ages. However, the concept of a national flag did not come about until the 18th century. And it wasn't until the 19th century that English people cared to differentiate between the Union Jack flag and the flag of their own specific country with the Red Cross. 
The St Georges day flag is thought to go right back to 1188 when the kings of England and France decided on crosses for their symbols ahead of a crusade. While the English king chose a white cross and the French one a red cross, England later switched to a red cross on white as a national symbol, though it's not clear when. The Red Cross was later used by English soldiers in several battles dating right through to the 1300s. Edward I (1272 -1307) is the monarch credited with making the cross a national emblem. Additionally, St George became a popular warrior saint during the crusades which meant by the end of the 1400s, the flag was being used to represent English monarch Henry VII as 'St George's banner'.
The first recorded use of St. George’s Cross as a maritime flag, in conjunction with royal banners, dates to 1545.