jquery calendar not working properly

Hi,

I want to change the appearance of jquery calendar

here is the code

body {
font-family: "Trebuchet MS", "Helvetica", "Arial", "Verdana", "sans-serif";
font-size: 62.5%;
}

if i apply this code jquery calendar is fine with small size but it affects the entire body of page.

i want to apply that only on date picker.

i tried this code

#datepicker {
font-family: "Trebuchet MS", "Helvetica", "Arial", "Verdana", "sans-serif";
font-size: 62.5%;
}

but not working what's the correct code.

Regards

Baiju