DateLastModified for web pages

[tucotuco]

Page(s) where issue occurs
All TWDG pages

Issue description
@ArthurChapman suggest, "I notice that the Darwin Core Quick Reference Guide (https://dwc.tdwg.org/terms/) does not have a date on the Web page. It should."

It seems to me that this is actually an important thing for every TDWG web page to have a date last modified.

[peterdesmet]

I’m not sure how to display the date on the page, but every page on www.tdwg.org does have an “edit this page” link, where you can see the latest commit date for the file, as well as what changed.

Pages on dwc.tdwg.org do not have this, but everything is under version control too, so the modified date can be retrieved.

[ArthurChapman]

It makes it very difficult to cite a page in a publication without a "Last modified" date clearly visible. For example, anyone wanting to cite the Darwin Core Quick Reference Guide ends up having to cite just TDWG n.dat. This is not good practice, and certainly not for a Standards organization.

[ArthurChapman]

The page I was particularly looking at was https://dwc.tdwg.org/terms/ where there is no "edit this page" link on the page. One can find a date under "Namespace Policy" but it should be easier for the general punter.

[peterdesmet]

While I agree it could be improved, for citing a page one could use the current date as in “accessed on yyyy-mm-dd”?

[peterdesmet]

I quickly looked whether Jekyll (the static website generator for tdwg.org and dwc.tdwg.org) can retrieve the last committed date.

• The plugin github-metadata (whitelisted by GitHub pages) does not support it
• The plugin last-modified-at does, but is not whitelisted by GitHub pages so won't work there. There is a request for it Whitelist plugin request: jekyll-last-modified-at github/pages-gem#838

@ArthurChapman note that https://dwc.tdwg.org/terms/ will get a edit this page link in the near future