Может быть, это то, что вы ищете:
import pandas as pd
df = pd.DataFrame({'Year': [2015, 2015, 2015, 2016, 2016],
'Quarter':[1, 2, 3, 4, 1]})
df['Year'] = df['Year'].astype(str)
df['Quarter'] = df['Quarter'].astype(str)
df['Time1'] = df['Year'] + '-Q' + df['Quarter']
df['Time2'] = df['Year'] + 'Q' + df['Quarter']
df['Time3'] = df['Year'] + ':Q' + df['Quarter']