[jira] [Created] (ARROW-15948) [C++] strptime rolls-over dates not in range for current month

["Dragoș Moldovan-Grünfeld (Jira)" <ji...@apache.org>]

Dragoș Moldovan-Grünfeld created ARROW-15948:
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             Summary: [C++] strptime rolls-over dates not in range for current month 
                 Key: ARROW-15948
                 URL: https://issues.apache.org/jira/browse/ARROW-15948
             Project: Apache Arrow
          Issue Type: Bug
          Components: C++, Python, R
            Reporter: Dragoș Moldovan-Grünfeld


I noticed some potentially unexpected behaviour when converting from string to date. Days that are out of bounds for the given month are rolled over into the following month.

I think the expected behaviour would be to either error (Python) or return NULL/NA (R), but not to roll over dates in the following month.
{code:r}
library(arrow, warn.conflicts = FALSE)
library(lubridate, warn.conflicts = FALSE)
library(dplyr, warn.conflicts = FALSE)

df <- tibble::tibble(string_date = "1999-02-30")

# base R returns NA
df %>% 
  mutate(date = strptime(string_date, format = "%Y-%m-%d"))
#> # A tibble: 1 × 2
#>   string_date date  
#>   <chr>       <dttm>
#> 1 1999-02-30  NA

# arrow rolls over the 30th of February into the 2nd of March
df %>% 
  arrow_table() %>% 
  mutate(date = strptime(string_date, format = "%Y-%m-%d")) %>% 
  collect()
#> # A tibble: 1 × 2
#>   string_date date               
#>   <chr>       <dttm>             
#> 1 1999-02-30  1999-03-02 00:00:00
{code}
Thanks Alenka, Joris and Rok for helping me with the Python examples: 
pandas:
{code:python}
>>> import pandas as pd
>>> pd.to_datetime("1999-02-30", format="%Y-%m-%d")
...
ValueError: time data 1999-02-30 doesn't match format specified
{code}
datetime:
{code:python}
>>> import datetime
>>> from datetime import datetime
>>> datetime.strptime("1999-02-30", "%Y-%m-%d")
...
ValueError: day is out of range for month
{code}
arrow:
{code:python}
>>> import pyarrow.compute as pc
>>> print(pc.strptime("1999-02-30", format="%Y-%m-%d", unit="s"))
1999-03-02 00:00:00
{code}



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