[Zope] Int to String

Im working with folders wich the ids are the years (2000, 1999 and so on). Im trying to list a folder using the following code: <dtml-with ZopeTime> <dtml-let ano="year()"> <dtml-in expr="ano.objectValues()"> <dtml-var id> </dtml-in> </dtml-let> </dtml-with> The year() function returns an Int, so when I call 'ano.objectValues()' zope does not understand it, because it is waiting a string. How can I turn my Int into a string? Or how can I make this easier? Thanks for the aid