單身熟男 2008-08-29

。。。every 3 days 每3天一次

。。。every 4 days 每4天一次（每隔3天一次）

我為你狂耶 2008-08-29

1 every three days

2 every second day

Pinkeaz 2008-08-29

once every three days

polyester00123 2008-08-29

once in a three days period， 後者是 once per three days。