在循环中递增日期

I've done some reasearch but I did not find any issue. I try to increment a date in a loop in order to test if some files does exist. In fact I would like to make some user play each sevent days. When they played the file is created whith their IP and with the date. So we test in a loop if a file does exist with each date between this days. If it exist we return 1 else we return 0.I've done some reasearch but I did not find any