how to subtract one day from a date in pandas code example

Example: pandas subtract days from date

df['date1'] = df['date'] -  pd.to_timedelta(df['day'], unit='d')

print (df)
        date  day      date1
0 2015-10-10   23 2015-09-17
1 2015-12-19    9 2015-12-10
2 2016-03-05   34 2016-01-31
3 2016-09-17   23 2016-08-25
4 2016-04-30    2 2016-04-28