Issue Summary

User try to import CSV file with fields "Target start" and "Target end", which are used in Advanced roadmaps.
And user set the date value for these fields like "15/JUN/23" in CSV, as these require the date format 'd/MMM/yy' .

Then, if user account preference language is Japanese, below error occurs:

In Japanese:
[ 無効な日付の形式です。日付は 'd/MMM/yy' の形式で入力してください。; 無効な日付の形式です。日付は 'd/MMM/yy' の形式で入力してください。 ]

In English:[ Invalid date format. Please enter the date in the format "d/MMM/yy".; Invalid date format. Please enter the date in the format "d/MMM/yy". ]

And if user try to import with different date format like "15/6/23", above error not occurs.

If user account preference is English and date format is like "15/JUN/23", error not occurs.
If user account preference is English and date format is like "15/6/23", above error occurs.

These behavior is inconsistent.

This is reproducible on Data Center: (yes) / (no)

Steps to Reproduce

1. User account preference language is Japanese
2. Try to CSV import with date format "d/MMM/yy" like "15/JUN/23" for "Target start" and "Target end"
3. Above error occurs and import failed

Test files:
Account preference language: Japanese > Result: Error
CSV: CSVimport_Error-inJPN.csv
Config file: Log_Error-inJPN.txt
Log: Log_Error-inJPN.txt

Account preference language: English > Result: Error
CSV: CSVImport_Error-inENG.csv
Config file: configurationFile-Error-inENG.txt
Log: Log_Error-inENG.txt

Expected Results

Even the account preference language is Japanese, system should accept date format "d/MMM/yy"

Actual Results

Validation of date format for "Target start" and "Target end" are inconsistent based on user preference language.

Workaround

If user account preference language is Japanese, use date format like "15/6/23".
If user account preference language is English, use date format like "15/JUN/23".