# import necessary libraries
import pandas as pd
import arrow

# create sample series
dates = pd.Series(["2022-01", "2022-02", "2022-03", "2022-04"])

# use pandas date_range() function
new_dates = dates.apply(lambda x: 
                        arrow.get(x + "-04", "YYYY-MM-DD"))

# print the results
print(new_dates)