What occurred were a number of informal truces at various places along the Western Front. However, what needs to be remembered is that these truces did not extend throughout the theatre of war and there were still skirmishes occurring between Christmas Eve (December 24) and Boxing Day (December 27).
In various war diaries of the time there are hints of these events. From the The Bedfordshire Regiment in the Great War 1914 War Diary transcription:
24 Dec 1914 Relieved by Manchester Regt. at 8pm. Battn took over a section on their right from Dorset Regt. at about 9 pm. without any casualties. Wolverghem & Battn. Hd Qrs shelled by enemy. Reinforcements 69 R & File arrived.
25 Dec 1914 Christmas cards from Their Majesties the King & Queen distributed to all ranks of the Battn. Also present from Her R. Highness Princess Mary. Cold & frosty day. Quiet day. Germans semaphored over that they were not going to fire. Hard frost all day.
26 Dec 1916 Another quiet day. A little shelling by both sides. Some Germans came forward unarmed apparently with a view to friendly intercourse. A few shots fired in their direction as a hint to withdraw. Later, enemy shelled trenches & Wolverghem: damaged several rifles, but only wounded 1 man.The personal diary of Regimental Sergeant-Major George Beck, of 1st Warwickshire Regiment, included details of those days. An image of the diary pages from the Dorset History Centre along with a transcription was included in the August 24, 2014 article "Midland soldier's poignant war diary reveals Christmas truce of December 1914" in the Birmingham Post:
24th Dec 1914 - Point 63
Quiet day. Relieved 2nd R DUB FUS [Royal Dublin Fusiliers] in the trenches in the evening. Germans shout over to us and ask us to play them at football, and also not to fire & they would do likewise. At 2 a.m. (25th) A German Band went along the trenches playing “Home, sweet Home” and God Save the King which sounded grand and made everyone think of Home. During the night several of our fellows went over “No Man’s Land” to German lines & was given a drink & cigars.
25th Dec 1914 - Trenches St Yves
Christmas Day. Not one shot was fired. English and German soldiers intermingled and exchanged souvenirs. Germans very eager to exchange almost anything for our bully beef and jam. Majority of them know French fluently. A few men of the regiment assisted in burying the dead of the Somerset Light Infantry who were killed on 19.12.14. Fine frosty day. Very cold.
26th Dec 1914 - Trenches St Yves
Unofficial truce kept up and our own fellows intermingled still with the Germans. No rifle shots fired, but our artillery fired a few rounds on the German 3rd and 4th lines and Germans retaliated with a few rounds on D Coys (Company’s) trenches. Two wounded.
In 1984 John McCutcheon wrote the song "Christmas in the Trenches" that poignantly described the scenes and thoughts through the eyes of a fictitious soldier named Francis Tolliver.
For Canadians the version by John McDermott is probably most familiar to us.
So during this Christmas season, sometime between doing your Christmas shopping and attending those parties, take a moment to remember all those affected by war regardless of the side they were on during the conflicts.