D. C. Donahue 
Glimpse from Christmas Past [EPUB ebook] 

While doing some last minute shopping on Christmas Eve a man has a magical experience. He watches a child preparing to get on Santa’s lap through a shop window and is reminded about a special Christmas memory. When the child gets down Santa makes eye contact with the man and they are immediately taken back to a moment they had shared (in his past). So the story unfolds as he stares through a window of time at a Glimpse from Christmas Past