According to Illicit Encounters.com, the last Friday before Christmas and final week is the one when people choose to have the most affairs before families are forced together over the festive period.
Today is one of the most popular days for Christmas parties, giving cheaters a cover, when they're actually sneaking off to be with their other lover.
It is also the day when many mistresses receive their Christmas gift, which often costs four times more than the one men buy for their wife. Mistresses' gifts come in at a whopping £440, whereas wive's presents come in at £100.
Mistresses tend to get spoiled with a designer dress compared to wives who get gifts of perfume or beauty sets.
76% of the sites members said they would be cheating in the run up to Christmas
The vast majority of members (76%) said they would be cheating in the week before Christmas. 64% revealed that they would be using their Christmas event to cover for the fact that they would be with their mistress.
Mistress Gweneth Lee, 45, was treated to a £5,000 erotic photoshoot by a married lover - a multi-millionaire Danish shipping magnate - she met on IllicitEncounters.com.
Gweneth said: "He wanted some beautiful pictures of me he could look at over Christmas and New Year when he was marooned with his family - to remind me of all the fun times we had enjoyed together.
"So my Christmas present was the photoshoot of my dreams.
"He hired a top fashion photographer who took the most incredible pictures of me in various soft bondage poses. I do still cherish those pictures - they are incredibly sexy.
"It was a wonderfully imaginative gift - he was behaving just like Christian Grey in Fifty Shades of Grey."
Gweneth added: "My lover would return to his wife and family for Christmas and New Year and play the role of the dutiful husband, but by the first week of January he was dying to see me again. Two weeks of being dutiful is enough for anyone.
"That is why the first week of January is such a furtive time for affairs."
Gweneth started seeing married men on Illicit Encounters after the death of their husband Robert.
She knows how Christmas goes from both sides of the spectrum- from mistress and wife.
She said: "I would much rather be the mistress. The presents are so much better and they are chosen with much more loving care."
An IlicitEncounters.com spokesman said: "We are entering the busiest time of the year for affairs. Our members are out in the run-up to weeks of the year for dating in the run-up to Christmas with activity peaking every year on Mistress Day, the last Friday before the Christmas break.
"Lots of members do carry on seeing their lovers over the Christmas period, particularly on Boxing Day when lots of men use sporting activities as a cover story to sneak out for some fun with their mistress."