When you set "Reset Poll Stats Automatically" to "Yes" you have another option: "Reset Stats Date:". If you set it for 2013-09-07 01:00:00, for example, it means that on September 7th, at 01:00:00, the stats will be reset.
If you also chose to reset the stats every day (""Reset Stats Every: 1 DAYS."), then starting with September 7th, every 24 hours, at 01:00:00, they will be reset.
Don't forget to correlate the current server time with your computer time and please note that the data you reset will not be saved.