find the min & max value for the below query - response (4) by Gowtham

dieter, there is no values like '8Month', here i have changed the datas and column names but the scenario is same. for pil1 i want the matched value, if not then i want the immediate lesser value as like this for pil2 i need the matched value, if not then want the immediate greater value. after i found all this, i wanna to subtract both the dates.