CODE EXAMPLE FOR PYTHON

pandas convert date to quarter

df['quarter'] = pd.PeriodIndex(df.date, freq='Q')

         date quarter
s1 2018-03-22  2018Q1
s2 2018-03-22  2018Q1
s1 2018-06-22  2018Q2
s2 2018-06-22  2018Q2
s1 2018-09-22  2018Q3
s2 2018-09-22  2018Q3