Hi,

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Isn't the exchange rate between those two countries should remain unchanged overnight? Also, if you execute a call to that Web Service from a different ISP or another route, you will get different values.
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Don't know where this website is getting its exchange rates from.
Money market exchange rates vary by the minute twentyfour hours a day. On the other hand most banks set their 'tourist-rates' just once a day (and these vary between banks). IAC, the only 'real' exchange rate is what you get when you do the deal.

Regards,
Viv