business date and calendar libraries?

[Chris Withers]

Hi All,

I'm wondering what libraries people would use to answer the following 
questions relating to business days:

- on a naive level; "what's give me the last business day" (ie: skipping 
weekends)

- on a less-naive level; same question but taking into account public 
holidays

- on a horrific level; same question, but taking into account business 
days of a particular market (NYSE, LSE, etc)

cheers,

Chris