Originally Posted by
sbedelman
An amusing story from when they used to play it straight was a trip I took to Israel many years ago. Amex computed the forex rate based on the day of the transaction while Visa on the date it hit their system. In those days the system was still paper and it often took a couple of day or more for a transaction to make its way to the local bank and days more until they processed it with the result that charges often showed up with a posting date a week to two weeks after the actual charge. Well Israel was going through hyperinflation (prices everywhere were written on chaulk boards and changed hourly) so the upshot was that a week or two delay turned into a substantial discount. I can't remember the exact amount but it could easily have been 10-25%.
Back during the Asian currency crisis the rates were all over the place too. However the credit card companies and the merchants had a trick up their sleeves. They would wait days, or weeks or even months before officially posting the transaction. People here on Flyertalk were hopping mad and talking about lawsuits, but it turns out there is some fine print in the agreement we sign that allows them to do this.