I tested click through rates for blog posts on the front page of Google with and without dates in the URL:
- 2+ year old articles (2012), removing the date in the URL tripled traffic.
- for recent, same year (2014), date removal was a marginal difference either direction.
My advice would be, if your article has a long shelf-life (like an article comparing PHP's sync nature vs. Node's async nature, since this is doubtful to change), an old date can inappropriately put a shelf-life on your appeal.
If you're writing on the 1.0 release of Angular and how you got around an annoying issue, that date will save me from copy/pasting your solution :)
Wait, which blog systems don't automatically display a time stamp with each post?
Wordpress, Blogger, and Tumblr have been displaying time stamps on default themes since the beginning (although some require the user to mouse-over a truncated time-stamp, which is annoying but a compromise).
Of course you're right, most blogging systems do have a timestamp by default, which is why it's even more infuriating that people who are putting serious thought into their writing are purposefully hiding the date or don't even think about its importance when they choose a theme that doesn't include it.
For all the reasons cited by the OP I'd like to endorse the idea.
And don't make it half-date either. It's even more infuriating seeing something is written on "May 1st" with no year!