I feel better to correct the year first, then convert to datetime:
# identify the year as the last group of digits and prepend 19
corrected_dates = Dae.str.replace('(\d+)$',r'19\1')
# convert to datetime
pd.to_datetime(corrected_dates)
Output:
0 1949-08-10
1 1945-01-21
2 1947-09-15
3 1952-06-13
dtype: datetime64[ns]