def add_quincena_column(dfx, date_col_name):
    """
    Adding column with a distinction between the first and second half of the month (quincena)

    :param dfx: (dataframe) df without the quincena column added
    :param date_col_name: (string) name of the column that will be used as reference the create the new quincena column
    :return dfx: (dataframe) df with a column indicating the half of the month with the following format: %y-%m-qx (where 'x' stands for 1 or 2, depending on the month's half)
    """


    ## Creating support column to identify the half of the month
    dfx.insert(
        dfx.columns.to_list().index(date_col_name) + 1,
        'support_col_month_half',
        dfx[date_col_name].apply(lambda x: '1' if int(x.strftime('%d')) <= 15 else '2')
    )

    ## Creating quincena column
    dfx.insert(
        dfx.columns.to_list().index(date_col_name) + 1,
        'quincena',
        dfx[date_col_name].dt.strftime(date_format='%y-%m-q') + dfx['support_col_month_half']
    )

    ## Dropping support column
    dfx.drop(['support_col_month_half'], axis=1, inplace=True)


    return dfx