Date calculations

I'm building a LaTeX document that helps me to formulate quotations for my customers. Since I decided to offer monthly recurring payments I'd like to have payment dates calculated automatically starting from a specific one. Say, for example, that you have:

\today{}

then I need to have:

• \today +30 days
• \today +60 days
• \today +180 days

and so on...

Is that possible?

EDIT: I ended up using the package advdate because I obtained a more compact result to do this:

% Payment starts in 4 months.

% 1 chunk per month -> due date:
\begin{enumerate*}
...
\end{enumerate*}

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This answer would benefit from an example. –  Martin Scharrer Oct 16 '11 at 16:37

This is possible with the datenumber package

\documentclass{article}
\usepackage{datenumber}

\begin{document}

\setdatetoday
\setdatebynumber{\thedatenumber}%
In 30 days is \datedate

\setdatetoday
\setdatebynumber{\thedatenumber}%
In 60 days is \datedate

\setdatetoday

@microspino, if you run texdoc datenumber on a command line, you'll find out about a command \setdatenumber to start from arbitrary dates. –  Juan A. Navarro Nov 3 '10 at 16:03