Daylight Saving Time or Summer Time, which is GMT plus one in Ireland and the UK, was introduced on April 30 in 1916 in Germany and Austria-Hungary.
Over the years there have been many attempts to extend DST (GMT plus one in Ireland and the UK, GMT plus two in mainland Europe) throughout the entire year.
Moscow does not observe Daylight Saving Time. It made the change some years ago.
That Ireland and the UK are always an hour behind the rest of Europe means that a number of hours are lost during the day to do business with counterparts on mainland Europe. They are at work an hour earler than we are, more time is lost during lunchtime and then at the finish of business they have gone home an hour before Irish offices close.
The term GMT has now been replaced by UCT, Coordinated Universal Time.