If the reporting currency of your account is different from the currency with which you're paid, your AdSense earnings will be converted. We convert earnings from your reporting currency to your payment currency using the prevailing market rate on the day the payment is processed.
Every month, we use Bloomberg to determine the exchange rate between your reporting currency and your payment currency. Bloomberg is an industry-recognized interbank rate source and the rates are set two business days before the last business day of the month at 16:00 London time.
For example, in a case where you generated earnings over several months and then exceeded the payment threshold in August 2011, your September payment would use the rate as quoted on Bloomberg at 16:00 London time on August 29, 2011.
You can view the exchange rate for a payment by clicking that month's Earnings line item in your list of recent payments.
For checks, the processing date may be a few days before the check date, so the date you see in your account may not reflect the day the currency was converted. Due to local bank requirements, the processing date for EFT payments may be up to 10 days before the funds appear in your account.