I just noticed one can set his own Format for date-times in User Settings
which could cause the regex to fail because the setting
also has an effect on the displayed node creation time.
When not set, the default setting for the date format on PM currently is "%b %d, %Y at %H:%M %Z"
(i.e. 'Nov 13, 2005 at 01:23 CET').
Using "%b %d, %Y at %H:%M:%S %Z" to also show the seconds would still work.
"%b %d, %Y %H:%M:%S" or "%b %d, %Y %H:%M"
(i.e. 'Nov 13, 2005 01:23') to convert the time string into unix time (aka epoch seconds).