Police have released a recording of a woman who dialled 999 to check if it was still Christmas Day and to wish the call-taker a merry Christmas.
Hertfordshire Constabulary has put the call, taken on Boxing Day, on YouTube to remind people of the dangers of wasting police time.
In the call, made at 1.50am on December 26, the woman asks the call-taker if it is still Christmas Day, only to be told it is Boxing Day.
When he asks "Have you got an emergency?", she replies no, then adds: "I just wanted to say, quickly, an important message to you if you could pass it on, OK, thank you.
"Merry Christmas. Today is Christmas Day."
Hertfordshire Police said at the time the force had already received 45 calls and it was during a busy period.
A spokeswoman said the festive season, which includes New Year's Eve, is notoriously busy - last year, from 7pm on December 31 to 7am on January 1, calls increased by more than double the average for a normal Thursday to Friday night.
She said the force released the Boxing Day call to remind people before New Year's Eve that hoax calls can stop important 999 calls getting through, as well as diverting valuable resources away from genuine emergencies.
Jason Baxter, assistant manager at the Force Communications Room, said: "This kind of reckless behaviour could not only result in a criminal conviction for the foolish caller.
"It could also ultimately put other genuine callers' lives at risk while they wait for their call to be answered or for officers to arrive.
"Our message is making hoax calls like this is not funny or cool. In fact, the joke could be on you should we decide to release your call to
the public or even arrest you.
"As New Year's Eve approaches, I am asking people to think before they make that call.
"Is it a genuine emergency - immediate threat to life or property? If not, it is not a 999 call and may be something to ring the non-emergency number on.
"However, if it is not a matter for police at all, it's plain and simple - don't call us so we can keep the lines free for those who do need our help."
The maximum penalty for hoax call offences is up to six months imprisonment and a fine of 5,000, police said, and if it involves specifically wasting police time, the sentence can be up to seven years behind bars.
The Boxing Day recording can be heard on YouTube at http://www.youtube.com/watch?v=FqfyXgMjUwY.