On the 1st of January 1973, Britain joined what was then known as the European Economic Community, now known as the EU. Ireland and Denmark also joined on that day.
One other country that joined the EU the same year as Ireland (1973) was Denmark.
Denmark and Ireland.
The countries that fought in D-Day were US, Britain,France and Russia.
None is same as India (August 15th). The closest is Pakistan (on August 14th)
December 26th is known in Britain as Boxing Day, and in many other countries as St Stephen's Day.
The USA, Canada, Australia, New Zealand and many smaller countries were with Britain on D-Day.
Rupert's Land and the Northwest Territories were transferred from Britain to Canada on July 15, 1870. The Province of Manitoba was created by the Canadian government on the same day.
Christmas and Easter are the same but Britain doesn't celebrate Presidents day, Columbus day, Independence day or Thanksgiving.
Ireland.
Denmark.
As Canada was a dominion of the British Empire, it joined the war the same day Britain declared war on Germany and the Central Powers; the 4th of August 1914.
America, Britain, France, and maybe more
Great Britain, or the United Kingdom, doesn't celebrate an independence day.
It doesn't have a specific number. In 1973 it joined what was then called the European Economic Community. There had been 6 countries as members before that, but on the same day that it joined, both Ireland and Denmark joined, so there were then 9 countries in it. None of them could be said to be the 7th, 8th or 9th country to join. In 1993 the European Union officially came into existence, by which time there were 15 members, so they could all be said to have become members at the same time too.