There is a vacuum for changing date format of the date columns in Ubuntu 14.04, 16.04, 18.04 and following (18.10, 19.04, 19.10, 20.04). (Neither dconf, gconf nor gsettings works, there is no date-format setting option.)

There are some workarounds, see How to show full date and time in Nautilus/Files 3.6+ list view.

Bug reports are opened on Gitlab and Bugzilla, please add your comments or help if you have the expertise as there has been no progress for years!

With other problems, e.g. Bug #1152226 “nautilus no longer remembers view per directory” and View mode setting should persistent for each directory, Nautilus is more and more user-UNfriendly and a switch to Nemo or other alternative file browser like Thunar is to consider.

ONLY Ubuntu 17.04 & 17.10 in a terminal (not in 18.04):

• gsettings set org.gnome.nautilus.preferences date-format iso


• gsettings set org.gnome.nautilus.preferences date-format locale


• gsettings set org.gnome.nautilus.preferences date-format informal
  
  Credit goes to Pablo Bianchi, see his comment.

For Caja (Mate 17.04): See other answer

Only works up to Ubuntu 12.04, maybe 13.10 (not 14.04 and 16.04):

Install dconf-editor (available in the normal repository), navigate to:

org>gnome>nautilus>preferences>date-format, then click on the field "value" beside the date-format field and a drop-down menu appears with the three choices:

• locale = Tue 12 June 2012 17:12:34 PHT


• iso = 2012-06-12 17:12:34


• informal = Today at 5:12:34 PM or Tuesday, June 12 2012 5:12:34 PM

I chose iso and am happy.