Why are the Hatter and the March Hare having an endless tea party?

In the book, Alice's Adventures in Wonderland, Alice and the Hatter have a long conversation about time, during the mad tea party. During this conversation, the Hatter explains that Time is a person, and if you get on with him, he can fix the time of day make it whatever time you like.

'....Now, if you only kept on good terms with him, he'd do almost anything you liked with the clock. For instance, suppose it were nine o'clock in the morning, just time to begin lessons: you'd only have to whisper a hint to Time, and round goes the clock in a twinkling! Half-past one, time for dinner!'

Unfortunately, it emerges that the Hatter has upset Time, by mangling the meter of a song he was singing at a concert given for the Queen of Hearts.

Well, I'd hardly finished the first verse,' said the Hatter, when the Queen jumped up and bawled out, "He's murdering the time! Off with his head!"'

As an act of revenge, Time has arranged things so that it is always six o'clock, and therefore always tea time. Thus the Hatter, the Dormouse and the March Hare are stuck in their never-ending tea party.