def change_start_date(dictionary_with_temporal_distribution):
    unsw_mid_year_end_date = datetime.date(2015, 7, 12)
for k in list(dictionary_with_temporal_distribution['C-STD-B&M-SUM'].keys()):
    dictionary_with_temporal_distribution['C-STD-B&M-SUM'][
        unsw_mid_year_end_date + timedelta(days=k)
        ] = dictionary_with_temporal_distribution['C-STD-B&M-SUM'][k]
Change multiple keys from dictionary, while doing timedelta operation in Python