import re
date_reg_exp2 = re.compile(r'\d{2}([-/.])(\d{2}|[a-zA-Z]{3})\1(\d{4}|\d{2})|\w{3}\s\d{2}[,.]\s\d{4}')
matches_list = [x.group() for x in date_reg_exp2.finditer("23-SEP-2015 and 23-09-2015 and 23-09-15 and Sep 23, 2015")]
print matches_list
aW1wb3J0IHJlCmRhdGVfcmVnX2V4cDIgPSByZS5jb21waWxlKHInXGR7Mn0oWy0vLl0pKFxkezJ9fFthLXpBLVpdezN9KVwxKFxkezR9fFxkezJ9KXxcd3szfVxzXGR7Mn1bLC5dXHNcZHs0fScpCm1hdGNoZXNfbGlzdCA9IFt4Lmdyb3VwKCkgZm9yIHggaW4gZGF0ZV9yZWdfZXhwMi5maW5kaXRlcigiMjMtU0VQLTIwMTUgYW5kIDIzLTA5LTIwMTUgYW5kIDIzLTA5LTE1IGFuZCBTZXAgMjMsIDIwMTUiKV0KcHJpbnQgbWF0Y2hlc19saXN0