python find and fix dates

I have a datafile with dates in a DD-MMM-YY format, but I need to make them into a DD-MMM-YYYY format

Quick Code

Note use of groupsize within the regex.

import re
a="tim,123,12-Jan-65,1-Feb-13,a,b,c,d,e"
print ("dataline is     {}".format(a))
dte=re.compile("([0-9]{1,2}[-][A-Za-z]{3}[-][0-9]{2})")

all_dates=dte.findall(a)
for bad_date in all_dates:
    fix_date=bad_date[:-2]+'20'+bad_date[-2:]
    print("\t\treplace {} with {}".format(bad_date,fix_date))
    a=a.replace(bad_date,fix_date)

print ("dataline is now {}".format(a))