when is the union jack called the union jack
Union Jack The terms Union Jack and Union Flag are both historically correct for describing the de facto national flag of the United Kingdom. Whether the term Union Jack applies only when used as a jack flag on a ship is a modern matter of debate.[9]
Union Jack The origins of the earlier flag of Great Britain date back to 1606. James VI of Scotland had inherited the English and Irish thrones in 1603 as James I, thereby uniting the crowns of England, Scotland, and Ireland in a personal union, although the three kingdoms remained separate states. On 12 April 1606, a new flag to represent this regal union between England and Scotland was specified in a royal decree, according to which the flag of England (a red cross on a white background, known as St George's Cross), and the flag of Scotland (a white saltire on a blue background, known as the Saltire or St Andrew's Cross), would be joined together, forming the flag of England and Scotland for maritime purposes. King James also began to refer to a "Kingdom of Great Britaine", although the union remained a personal one.