DataTable sorting by timestamp is alphabetic, not "calendaric"

[jimklimov]

Jenkins and plugins versions report

LockableResources-2.18 custom built with table sorting commit added (as of PR #470 d07b8c8)
Jenkins LTS 2.387.2

What Operating System are you using (both controller, and any agents involved in the problem)?

Linux server
Windows browser (Firefox)

Reproduction steps

Open lockable resources page with several items locked in different months (can be prepared via API LR.setReservedTimestamp() call)

Click table header to sort by timestamp

Expected Results

Sorting is by actual timestamp (date-time) value, ascending or descending as chosen.

Defined (non-null) timestamps are always first.

Actual Results

Sorting seems to be by months naming (alphabetic).

In descending order, I see Mar-Jan-Apr:

In ascending order, I see lots of empty lines (no timestamp) and then some months.

Anything else?

No response

[jimklimov]

As a side note for possible inspiration: just noticed that Jenkins plugin update table (not sure if it uses DataTables too?) has correct sorting by "Released" column - despite writing "20 hr ago" or "1 day 1 hr ago", it sorts not alphabetically by such text but by actual time range length.