Originally Posted by Happy

Did you use the Transaction Dates or the Posting Dates?

AFAIK, Chase use Posting Dates for the conversion.

Same as FIA card - it used Posting Dates. I had some charges made in Japan that the merchant for whatever reason did not send in the charges until 6 weeks later (they were all small amount purchases at the department store's basement supermarket). Yen during that time period jumped almost 6% so the conversion was against me but C'est la vie.

FWIW, the rates with Visa also seem always a tiny bit higher than the Mean historical rates I found on XE - but the variance is so small I dont think it is worth to sweat about.