Did the WWI XMAS kick about between Germany & England really happen?

It's BS, my great grandfather fought in the somme and he didn't stop slaughtering germans until it was time for tea. He didn't care if it was Christmas or easter, kill first then bangers and mash. It makes sense to have a ceasefire and a sing song, get them on open ground have a mate mow them down then snatch their grub and hock. Thats what i would have done.