Problem in windows recipe tutorial

Hemakshi

I am doing windows recipe after join, prepare and group recipe using learning paths. the purchase_date in my tx_windows is not of required type. it is of string type. It is string and because of that i cannot perform certain window recipe functions on the column. So i did the prepare recipe and followed each and every step in the tutorial on dataiku academy. In the extract date components step after delete and rename columns step in prepare recipe tutorial, in the picture shown it is clearly seen that after extracting date components step, the column which i need: purchase_date has changed its type from string to date but mine is not changed and i haven't miss any step