A study by tanning brand St Tropez linked women's countenance with the activity of the day.

While 12 per cent of female workers consider Wednesday or mid-week the most stressful day in a typical week, by Friday, the women show a rosy glow, likely a byproduct of the sex they had on Thursday.

The high stress level on Wednesday is often because of too much pending tasks on hand that they have to work even during lunch hour. Thus, 25 per cent of the female workers have a sugar-laden snack to improve their mood and energy.

Another factor behind the haggard Wednesday look is the booze the women took during the previous weekend which takes a few days to manifest, but processing the toxins in alcohol and sugar strains the body.

Wednesday is also often preceded by a sleepless Monday night, which takes 48 hours to show on the face.

The result is a drop in energy level which causes them to look their oldest by 3:30 p.m.

"Combine the highest stress levels of the week on a Wednesday with the natural mid-afternoon slump and it seems that's why women can look older than their years," The Telegraph quoted Nichola Joss, a St. Tropez skin expert.

She added that with the drop in stress level and the mid-week slump passed, by Thursday evening, women workers are mostly feeling amorous which could led to sex with their partners.

Other than stressful workplace situations and alcoholic and sugary inputs, Ms Joss pointed to lack of sleep as a contributor to ageing. While the recommended average sleeping time is from 7 to 8 hours, most British women on sleep an average of 6 hours and 43 minutes daily.

Going by these findings, this favourite mirror scene in the fairy tale Snow White and the Seven Dwarves would likely yield a different response if asked the question "Mirror, mirror on the wall, who's the fairest of them all?"

Perhaps the mirror would reply back, "It depends on what day of the week."