from datetime import date
import pandas as pd
from datetime import datetime
Dae = pd.Series(["10Aug49","21Jan45","15Sep47","13Jun52"])
x =[]
new_list = []
for i in Dae:
i = datetime.strptime(i,"%d%b%y").date()
if date.today() <= i:
i = i.replace(year=i.year - 100)
new_list.append(i)
print(new_list)
[datetime.date(1949, 8, 10), datetime.date(1945, 1, 21), datetime.date(1947, 9, 15), datetime.date(1952, 6, 13)]