Field Validation on Date field - Multiple languages

 Hi All,

We have a field validation rule on one of the date fields on opportunity object that actually checks and throws error if that date is greater than today's date, if the opportunity is at certain sales stage(In this case Closed stages). We also have various sales processes with their own sales stages. The problem we are having is that this validation rule is not working with the users whose language is not English. Below is the expression that we are using:

(IIf([<SalesStage>]='Closed/Won' AND [<CloseDate>]>Today(),'Error',IIf([<SalesStage>]='Closed/Lost' AND [<CloseDate>]>Today(),'Error',IIf([<SalesStage>]='Awarded' AND [<CloseDate>]>Today(),'Error',IIf([<SalesStage>]='Decision' AND [<CloseDate>]>Today(),'Error',IIf([<CloseDate>]<[<IndexedDate0>],'Error',IIf([<CloseDate>]>[<dAnticipated_Order_Date_I_ITAG>],'Error',[<CloseDate>])))))))