I dont think date and time in the same field (of date data type) is supported in shapefiles. You can add two fields, one for date and one for time. Example how to get date, use datetime.datetime.strptime:
Return a datetime corresponding to date_string, parsed according to
format
import arcpy, re
from datetime import datetime
#import locale
#locale.setlocale(locale.LC_ALL, 'en_US') #Otherwise 'OCT' was not recognized since my locale is SWE = 'OKT'
fc = r"X:\blabla2016OCT151234.shp" #Change
datefield = 'Date123' #Change
ix_first_digit = re.search("\d", fc).start() #Find first digit (so path cant contain digits or you need to change the code)
datestring = fc[ix_first_digit:ix_first_digit+9] #Slice from first occurence of digit and then nine more chars
date = datetime.strptime(datestring, '%Y%b%d') #See: https://docs.python.org/2/library/datetime.html#strftime-and-strptime-behavior
#Calculate field using da.UpdateCursor
with arcpy.da.UpdateCursor(fc, datefield) as cursor:
for row in cursor:
row[0]=date
cursor.updateRow(row)