datetime.datetime.strptime get day error

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-04-09.09:55:31.623>
labels = ['3.7', '3.8', 'type-bug', 'library', '3.9']
title = 'datetime.datetime.strptime get day error'
updated_at = <Date 2022-01-01.15:45:08.343>
user = 'https://bugs.python.org/zhanying'

bugs.python.org fields:

activity = <Date 2022-01-01.15:45:08.343>
actor = 'andrei.avk'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-04-09.09:55:31.623>
creator = 'zhanying'
dependencies = []
files = []
hgrepos = []
issue_num = 40236
keywords = ['patch']
message_count = 11.0
messages = ['366039', '366046', '366055', '366062', '366070', '366100', '366101', '374480', '374486', '409448', '409464']
nosy_count = 6.0
nosy_names = ['belopolsky', 'eric.smith', 'karlcow', 'p-ganssle', 'zhanying', 'andrei.avk']
pr_nums = ['30318']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue40236'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8', 'Python 3.9']