You can compare lexicographically with the conditional construct [[ ]] in this way:
[[ "2014-12-01T21:34:03+02:00" < "2014-12-01T21:35:03+02:00" ]]
From the man:
[[ expression ]]
Return a status of 0 or 1 depending on the evaluation of the conditional expression expression.
New update:
If you need to compare times with different time-zone, you can first convert those times in this way:
get_date() {
date --utc --date="$1" +"%Y-%m-%d %H:%M:%S"
}
$ get_date "2014-12-01T14:00:00+00:00"
2014-12-01 14:00:00
$ get_date "2014-12-01T12:00:00-05:00"
2014-12-01 17:00:00
$ [[ $(get_date "2014-12-01T14:00:00+00:00") < $(get_date "2014-12-01T12:00:00-05:00") ]] && echo it works
it works