User blog comment:Na299/Ways of Gold Farming/@comment-194.149.101.199-20150605101822/@comment-180.214.232.70-20150605130741

I couldn't find any info on the internet, but based on calculation, you'll need 10 days to complete each event, there are 3 cars, so 3x10 days each = 30 days, so you should've started the event right on june 4, because on july 4, the cars will be available for sale.