How AdSense determines the exchange rate for your earnings
We convert advertisers’ payments from their currencies to your payment currency using the prevailing market rate from the day before the ads were shown. We get our rates from major banks, and other industry-recognised rate sources.
For example, let's say that you get paid in euros, and an advertiser purchases ads on your site using US dollars on 15 August. We'll then calculate your earnings using the dollar to euro exchange rate from the end of 14 August.
The exchange rate for reports
We convert currencies in reports in the same way. This means that reports in your payment currency should reflect the amount that you'll be paid. Reports in a different currency reflect the amount that you'd be paid if you were paid in that currency.