I’ve tried both – both bulk action, as well as individual post, and neither “sticks”. After picking the date and time, is there anything else I need to do, other than click away and/or press “Enter”?

Ok, so one thing I just realized I wasn’t doing, was “ticking” (or selecting) the post I wanted to update the date/time. Duh!

However, after doing that, and updating the date/time, I got the following error:

WordPress database error: []
UPDATE wp_posts SET post_date = ‘2017-10-29 10:00:00’, post_date_gmt = ‘2017-10-29 10:00:00’, post_modified = ‘2017-10-29 10:00:00’, post_modified_gmt = ‘2017-10-29 10:00:00’ WHERE ID = 101

After going back to the posts page, it looks like it DID update the date/time, so that’s good, but the error will likely “scare” a few people!

Thanks for your help!