NEW YORK (Reuters) - 'Tis the season for calling in sick, especially if you're not sick at all.

One in three workers has called in sick when they're not in the past year, and the end-of-year holiday season brings a rash of phony absences, experts and studies say.

Harried workers are juggling shopping, holiday preparations and family obligations this time of year, on top of perhaps having run out of the year's legitimate vacation days, they say. And the mornings after holiday parties don't help.

"We do know just anecdotally in dealing with employers that there certainly is a higher rate ... associated with holidays, catching up on shopping, or spending time with family and friends," said Jennifer Sullivan, spokeswoman for CareerBuilder.com, which conducts an annual survey of employee absenteeism. "You do see a higher incidence."

The firm's survey, released this week, showed 32 percent of workers said they called in sick when they felt fine at least once in the last year, and one in 10 said they did so three times or more.

Women were more likely to take a sick day when they are not sick than men, by 37 to 26 percent, the survey said.

But be careful. The same survey showed 27 percent of hiring managers have fired a worker for calling in sick without a legitimate reason.

"The worst part is, if you lie and they see you out at a sporting event or shopping or you run into somebody you know, then it brings your trustworthiness into question," said Sullivan.

The trick is doing it right, writes Ellie Bishop, author of "The Sick Day Handbook" that is chock-full of tips for taking a not-really-sick day.

She suggests if you're claiming a migraine headache, know there are two kinds, cluster and classic. Claiming Lyme disease is handy, because one symptom is irritability. Conjunctivitis and irritable bowel syndrome are good excuses because no one wants to hear about the symptoms.

HOLD YOUR NOSE

Call in with your excuse to a co-worker early, before the boss arrives, clear your throat for five minutes beforehand and hold your nose as you speak, she suggests.

Never make up anything that might need to be proven, like a doctor's appointment or a trip to a hospital emergency room, she writes.

Only try it two or three times a year and, above all, remember your lie, she adds.

"I think we can get away with a lot more than we think we can," she said.

If you do get caught, Sullivan added, employers tend to be a little bit more understanding than they once were.

"If people just need a mental health day or they just need to get away from the office, I think employers are much more understanding of that than they would have been 10 or 20 years ago," she said.

"That's a trend that has strengthened certainly over the last few years, where people are just more aware of the work-life balance," Sullivan added, "because you tend to have more productive workers and you have happier workers if they're able to maintain that balance between their commitments at the office and their commitments at home."

The CareerBuilder survey was conducted online by Harris Interactive in September among 1,650 workers and 1,150 hiring managers nationwide. CareerBuilder.com is owned by Gannett Co. Inc., Tribune Co. and The McClatchy Co.>.