If you want to add specific class names to certain days of the week using the jQuery UI datepicker, you can utilize the css nth-child selector.
For instance, if Sunday is the first day of your calendar week, the third cell represents Tuesday, which can be highlighted with the following code:
.ui-datepicker-calendar tbody tr td:nth-child(5n+3) a {background: #FC0;}
In this scenario, only the second table cell will change as the formula (5n+3) targets every fifth cell starting from the third. The sequence follows 3, 8, 13, 18, 23, 28 etc., but since there are only seven days in a week, no other cells are affected.
This resource provides a comprehensive explanation on how the nth child function operates - http://css-tricks.com/how-nth-child-works/
Using the nth-child formula in jQuery ensures a consistent outcome across different browsers.