Generally, I believe it is better to use DATE(2009,1,2) instead
of --"1/2/2009" because the interpretation of the latter depends Regional
and Language settings.

What about TIME(13,0,0) v. --"13:00"?

In my (US) Regional and Language settings, ":" is the only separator in the
drop-down list.

But I presume it is a drop-down list for a reason. Do some languages use a
differ time separator, at least optionally?

Do some languages specify time in a different order than hh:mm?