If you've got a lunch date coming up this Wednesday, researchers recommend that you push it back a few days. Experts say that women look their oldest at 3:30pm every Wednesday.

They explain that midday Wednesday is when energy levels plunge, work stress peaks and the effects of any weekend part nights finally start to kick in.

Recent research reveals that more than one in ten women (12 percent) say that Wednesday is the most stressful day in a typical week.

However, the day after is much better. Researchers say that Thursday is the day women are most likely to have sex.

Getting busy on Thursday would then give women a youthful, rosy glow which could explain why women feel so happy on Friday. According to the new survey, 60 percent of women say Friday is their happiest day of the week.

The research also reveals that a fourth of women feel stressed several times a week, while 19 percent say that they will often work through Wednesday's lunch hour.

The latest study, conducted by tanning brand St. Tropez, found that two thirds of women experience a "slump in energy levels" mid-afternoon every Wednesday. The survey also found that the plummeting energy levels forces a quarter of women to eat a sugary snack to boost their mood and energy.

"It's fascinating that 3.30pm on a Wednesday is the time women look their oldest," said Nichola Joss, St. Tropez skin expert, according to The Telegraph.

"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," Joss added.

She also said that a woman's sex life can have a big impact on how she feels.

"Many women credit a healthy sex life for keeping them looking and feeling young," Joss said.

"As the mid-week slump passes and stress levels begin to decrease, it's fascinating that Thursday is the evening they are most likely to feel amorous," she explained.

The survey found that 46 percent of women indulge in a alcoholic beverage during the weekend. Researchers say that this is another reason why women look their oldest in the middle of the week.

Joss said that it normally takes a few days for the negative effect of the party-filled weekend to show.

"Processing the toxins in alcohol and sugar can put strain on the body," she said. "It can take up to 72 hours for the visible effects of alcohol to show, so the effects of drinking on the weekend may not present themselves until Wednesday afternoon."

Researchers found that the dread of going back to work has also given many women sleepless nights. According to the survey, 37 percent of women reported Monday night as being the time when they are most likely to get a bad night's sleep.

A lack of sleep on a Monday does not bode well for how the skin will look on Wednesday," Joss said. "The effects of a lack of sleep can take 48 hours to show on the face, so if many women sleep badly on Monday they will look their oldest on Wednesday."

Joss recommends that women get seven to eight hours of sleep at night for maximum anti-aging benefits.

"Too little and your skin cells can't rejuvenate, too much can result in puffy, older looking skin," she said.

She also said that women should have a skin care regimen that they stick to every day of the week.

"Even if a woman doesn't wear make-up, it's essential to cleanse the face of build up from everyday pollution," she said. "Letting these build up clogs the skin making it duller and drier, and superficially older."