Matching possible date elements in range - regex

Question

I'm having difficulty matching other cases for a date range. The end goal will be to extract each group to build an ISO 8601 date format.
Test cases
May 8th – 14th, 2019
November 25th – December 2nd
November 5th, 2018 – January 13th, 2019
September 17th – 23rd
Regex
(\w{3,9})\s([1-9]|[12]\d|3[01])(?:st|nd|rd|th),\s(19|20)\d{2}\s–\s(\w{3,9})\s([1-9]|[12]\d|3[01])(?:st|nd|rd|th),\s(19|20)\d{2}
regexr
I would like to be able to capture each group regardless if it exists or not.
For example, May 8th – 14th, 2019
Group 1 May
Group 2 8th
Group 3
Group 4
Group 5 14th
Group 6 2019
And November 5th, 2018 – January 13th, 2019
Group 1 November
Group 2 5th
Group 3 2018
Group 4 January
Group 5 13th
Group 6 2019

Answer 1

To capture the empty string if the group doesn't match otherwise, the general idea is to use (<characters to match>|)
Try this one:
([A-z]{3,9})\s((?:[1-9]|[12]\d|3[01])(?:st|nd|rd|th))(?:, (?=19|20))?(\d{4}|)\s–\s([A-z]{3,9}|)\s?((?:[1-9]|[12]\d|3[01])(?:st|nd|rd|th))(?:, (?=19|20))?(\d{4}|)
https://regex101.com/r/4UY0WE/1/
When trying to capture the month (the first group), make sure to use [A-z]{3,9} rather than \w{3,9}, otherwise you might match, eg, 23rd rather than a month string.
Separated out:
([A-z]{3,9}) # Month ("January")
\s
((?:[1-9]|[12]\d|3[01])(?:st|nd|rd|th)) # Day of month, including suffix ("23rd")
(?:, (?=19|20))? # Comma and space, if followed by year
(\d{4}|) # Year
\s–\s #
([A-z]{3,9}|) # same as first line
\s?
# same as third to fifth lines:
((?:[1-9]|[12]\d|3[01])(?:st|nd|rd|th))
(?:, (?=19|20))?
(\d{4}|)

Answer 2

This one saves some space by consolidating some of the groupings.
Try it here
Full regex:
([A-z]{3,9}) ((?:[1-9]|[12]\d|3[01])(?:st|nd|rd|th))(?:, ((?:19|20)\d{2}))? [–-] ([A-z]{3,9}\s)?((?:[1-9]|[12]\d|3[01])(?:st|nd|rd|th))(?:, ((?:19|20)\d{2}))?
Separated by group (spaces replaced by \s for readability):
1. ([A-z]{3,9})
\s
2. ((?:[1-9]|[12]\d|3[01])(?:st|nd|rd|th))
3. (?:,\s((?:19|20)\d{2}))?
\s[–-]\s
4. ([A-z]{3,9}\s)?
5. ((?:[1-9]|[12]\d|3[01])(?:st|nd|rd|th))
6. (?:,\s((?:19|20)\d{2}))?
This method does not use lookups so is generally safe for any regex engine.