All TudoVemdaChina users, registered in our newsletter weekly (and you click any of the links in the newsletter), participate in a monthly draw of 10 U.S. dollars (payment made in reais)! But as the user is chosen?
During the month, the system receiving the clicks on newsletter and forming a list. At the end of the month, the system picks up the number of seconds since January 1, 1970 until the first second of the beginning of the month of the promotion, and uses this value to make some calculations very crazy ¹ and choose a number between the first and the last on the list. If the user winner not respond an e-mail with your contact, PayPal account or other payment method, the prize will be for the next on the list (or the first case the original winner is the last on the list).
¹ To whom it may concern, the user is chosen (in PHP) with the command:
ABS(CRC32((String)$datadoiniciopromocao))%$tamanholista + 1
where $datadoiniciopromocao is the number of seconds since January 1, 1970 until the first second of the beginning of the month of the promotion and $tamanholista is the number of members in the promotion.