product sales start/end

Can u plz tell me the code location for "product sales start/end date".i want to use those field as my on-line training start and end date nd time.but i want to remove the restriction of purchasing the training according to the value of those field.Can you plz help me out of this.

Thanks to not duplicate your posts

www.hikashop.com/en/forum/4-how-to/76244...-end-date.html#79440