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BUG: weekday incorrect for dates before 0000-03-01 #53738
Description
Pandas version checks
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I have confirmed this bug exists on the latest version of pandas.
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I have confirmed this bug exists on the main branch of pandas.
Reproducible Example
In [1]: pd.Timestamp('0000-03-01').weekday()
Out[1]: 2
In [2]: pd.Timestamp('0000-02-29').weekday()
Out[2]: 2Issue Description
pandas thinks that before Wednesday there was another Wednesday - my guess is that this was written by a French pupil trying to get an extra half-day off? 😄
Expected Behavior
I'd expect
In [1]: pd.Timestamp('0000-03-01').weekday()
Out[1]: 2
In [2]: pd.Timestamp('0000-02-29').weekday()
Out[2]: 1At least, that's what Rust's chrono gives:
use chrono::{NaiveDate};
fn main() {
let date_str = "0000-02-29";
let date = NaiveDate::parse_from_str(date_str, "%Y-%m-%d").unwrap();
let weekday_abbrev = date.format("%a").to_string();
println!("date: {:?}", date);
println!("Weekday (abbreviated): {}", weekday_abbrev);
}outputs
date: 0000-02-29
Weekday (abbreviated): TueLikewise, https://calculat.io/en/date/what-day-of-the-week-is/29-february-0000 gives it as Tuesday
Installed Versions
Details
INSTALLED VERSIONS
commit : 965ceca
python : 3.10.6.final.0
python-bits : 64
OS : Linux
OS-release : 5.10.102.1-microsoft-standard-WSL2
Version : #1 SMP Wed Mar 2 00:30:59 UTC 2022
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_GB.UTF-8
LOCALE : en_GB.UTF-8
pandas : 2.0.2
numpy : 1.24.3
pytz : 2023.3
dateutil : 2.8.2
setuptools : 67.6.1
pip : 23.0.1
Cython : None
pytest : 7.3.1
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : 8.13.2
pandas_datareader: None
bs4 : 4.12.2
bottleneck : None
brotli : None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : 3.7.1
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : 12.0.0
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : None
snappy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
zstandard : None
tzdata : 2023.3
qtpy : None
pyqt5 : None
None
Activity
MarcoGorelli commentedon Jun 20, 2023
From https://en.wikipedia.org/wiki/Determination_of_the_day_of_the_week#Sakamoto.27s_methods, it looks like the current method is only accurate if the year is greater than 1752
mcgeestocks commentedon Jun 20, 2023
take
jorisvandenbossche commentedon Jun 27, 2023
Just as confirmation with another tool, also Arrow (date.h) gives the same result as chrono: