At 47:15, Violet tells Cora, "We'll give her till the start of the grouse," referring to the start of the grouse hunting season on August 12.
Although it is not mentioned, the trans-Atlantic ocean liner RMS Empress of Ireland sank in the Gulf of St. Lawrence; with 1,012 lives lost, 500 less that were lost on the Titanic two years earlier.
Although it is not mentioned by Branson, in May, 1914, when the episode takes place,
Britain's House of Commons passed Irish Home Rule.
While many plot points in Downton Abbey reflect actual events, there was no Skipton and Ripon by-election in May 1914.