According to a survey of 2,000 UK adults conducted by Kwik Fit, today is the day we're all most likely to feel the effects of the Christmas Comedown – and it's set to peak at 2.59pm this afternoon.
If you're hitting the road to make your way home from spending Christmas with rellies, tensions are predicted to come to a head shortly before 3pm.
As for the top triggers for festive flare-ups, these include criticism from family members (18 per cent), inappropriate behaviour (15 per cent), people not helping out around the house (14 per cent), mess and clutter (12 per cent) and being given bad directions when travelling (12 per cent).
The research also found that 'Moody Monday' is not only the day families expect they are most likely to row during the festive period (56 per cent), but also the day the attention of over a third will be turning to worries about over-indulgence and the year ahead.
I'm leaving that well aside because I'm still well in holiday mode and am not ready to start caring about the size of either my bank balance or my waistline.
But those of you who find your mind wandering from festivities are apparently likely to be mulling over financial worries (29 per cent), bulging waistlines (28 per cent), a post-Christmas anti-climax (14 per cent), returning to work (13 per cent) and not having properly relaxed (12 per cent).
The average Brit is estimated to be £470.21 in debt by 28th December, have put on 4.53lbs in weight and eaten six mince pies each. I don't even want to think about any of this. Although I'm pretty sure I'm about two mince pies down so that's breakfast sorted.
The study also found - unsurprisingly, in the light of all that - that forty per cent of us fantasise about going away for Christmas next year.
Paul Boulton, Retail Sales & Operations Director at Kwik Fit, said:
"Christmas is of course the most wonderful time of year, but it comes as no surprise that tempers can on occasion boil over in the car on the way back from several intense days of living at close quarters with family. These squabbles can be distracting for drivers at what is already tricky time of year to be on the roads, so we are urging families to take extra care when travelling home and try to extend the season of peace and good will to all men as long as possible."
Kwik Fit recommends putting your car through their free winter safety check before you hit the road to drive home after Christmas, but cautions that their technicians can't help resolve any simmering family disputes. That made me chuckle. Maybe they should employ relationship counsellors at this time of year?
Anyway, in the light of this study I plan to settle myself on the sofa - with the last of the Quality Street, of course - and I'll pretty much refuse to move until after 2.59pm - just in case.
So how will you be spending Moody Monday, and have tempers already started to fray?