This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Okay... does that mean that the actual XML document has 35 <day> elements, and you want to select the ones with number="7"? Or does it mean that you need to convert the day of the month to the day of the week? Or does it mean something else? I think you should clarify your requirements before you start implementing them.