awk '$2FS >="2017-02-21T11:09:41.000Z" && $2FS <="2017-02-23T11:09:41.000Z"'

awk 'convert_to_date($2FS,'EST') >="2017-02-21T11:09:41.000Z"
&& convert_to_date($2FS,'EST') <="2017-02-23T11:09:41.000Z"'

echo $TIMESTAMP | gawk '{print strftime("%c", $0)}'

# echo 0 | gawk '{print strftime("%c", $0)}'
Wed 31 Dec 1969 07:00:00 PM EST