you can use the following three steps:
step1: substr(variable,n1,n2) to get your year,month and day respectively, and then apply ddmmmyy format
step2: substr(variable,n1,n2) to get the rest parts ( " 00:00:00)"
then append the above two resultss together, you will get character ,
next you should transfer character into numeric
step3: apply datatimew.d format to your get your result,
In my options ,this method should be ok, I use this method in my clinical trials .hopefullly,you will get your results.