Is there a free/cheap service, accessible through a web service or simple HTTP/XML queries, that can convert from a currency to another, but with the exchange rate of a specific date in the past? Say I need to know how much 10 USD was in EUR on date March, 13, 2009. So far I've only found oanda.com offering this service to developers, but they cost 200$/mo, and my budget is lower.
ECB is cool! But it works if I need to convert from EUR to something. If I need to convert from GBP to something elase I'll have to find another time series :( Isn't there a service or time series provider to convert from any currency to any other currency, for a certain date? Like OANDA actually, just cheaper :)