Simplest standard way to print last bash command with timestamp

As you point out, history 1 prints the history command itself since that is the last command you ran. To get the previous one, you'd need history 2:

$ touch foo
$ history 2
$ history 2
19950  touch foo
19951  history 2

So, to get the previous command without counting history itself, pass it through head -n1:

$ history 2 | head -n1
19952  touch foo

Then, add the time stamp in whatever format you want (see man 3 strftime for available formats):

$ HISTTIMEFORMAT="%F %H:%m:%S " history 2 | head -n1
19959  2016-06-11 15:06:08 touch foo