import re
regex = re.compile(r"""
([ :]) # look for : and space as possible leading characters
([\"]?) # if there's a quote, disregard it
([0-9]{4}) # find the year
- # find the 1st dash
( # Group (4)
(
((0[13578] | (10|12)) # look for 31 day months
- # followed by the 2nd dash
(0[1-9]|[1-2][0-9]|3[0-1]) # and accept days up to 31
)
| # OR...
(02 # look for Feb
- # followed by the 2nd dash
(0[1-9]|[1-2][0-9])) # and accept up to 29 days
| # OR...
((0[469]|11)) # look for 30 day months
- # followed by the 2nd dash
((0[1-9]|[1-2][0-9]|30)) # and accept up to 30 days
)
) # closes (4)
([\"]?)([ \"]?)(\s)
""", flags=re.MULTILINE | re.VERBOSE)
test_str = ("This regex changes YYYY-MM-DD to \"[[YYYY-MM-DD]]\" for Obsidian\n"
"WORKS ON:\n"
"today: 2025-03-14\n"
"birthdays: 1966-06-19\n"
"Good Dates: 2022-12-31 and 2025-02-08\n"
"old-dates: 1492-01-01 old dates could be an issue, depends on how you use your vault!\n"
"no space after colon is ok:2023-07-08\n"
"standing alone and quoted is fine: \"2021-02-28\"\n"
"IGNORES:\n"
"my template version number has dots for separators (skip): 2025.12.02\n"
"No leading whitespace is questionable?2023-06-08\n"
"existing links (no leading : or space):\n"
" - [[2025-01-01]]\n"
"- [2025-01-01](https:123.com)\n"
" - \"[[2023-11-30]]\"\n"
" - [[\"2024-06-05\"]]\n"
"Not YYYY-MM-DD dates:- 2022-1-1 Euro date: 2022-31-12 or slashes: 2021/09/15\n"
"Bad date for month: 2022-02-30 2022-04-31 2022-06-31 2022-11-31 2022-03-32\n"
"Don't match serial numbers: 2015-12-3135-89\n")
subst = "$1\"[[$3-$4]]\"$18"
result = regex.sub(subst, test_str)
if result:
print(result)
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Python, please visit: https://docs.python.org/3/library/re.html