I am running Drupal 6, the last version by the time of writing.
I am getting this warnings when, updating / creating nodes, or when running the cron manually.
Warning: strtotime(): It is not safe to rely on the system’s timezone settings. Please use the date.timezone setting, the TZ environment variable or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected ‘America/Chicago’ for ‘CDT/-5.0/DST’ …..
The solution was pretty simple, just be sure to add in
/etc/php.ini the time zone where your server is.
In my case “America/New_York”.
So a snip of
; http://php.net/date.timezone date.timezone = America/New_York
Also be sure to restart Apache once that is done.