Shell Programming and Scripting

Just for completeness, here is a solution based on ksh93 version h or later.

Code:

#!/usr/bin/ksh93
#
# USAGE: diffdate start-date  finish-date
# 
# EXAMPLE: diffdate "Tue, Feb 19, 2008 08:00:02 PM" "Wed, Feb 20, 2008 02:19:09 AM"
#

SDATE=$(printf '%(%s)T' "$1")
FDATE=$(printf '%(%s)T' "$2")

[[ $# -ne 2 ]] && {
   print "Usage: diffdate start-date finish-date"
   exit 1
}

DIFF=$(($FDATE-$SDATE))

SECS=$(($DIFF % 60))
MINS=$(($DIFF % (60 * 60) / 60))
HOURS=$(($DIFF / (60 * 60)))

printf "%02d:%02d:%02d\n" $HOURS $MINS $SECS

exit 0

You can use the following :
It gives date difference in seconds.

T1='5:02:02'

T2='5:19:59'


h1=`echo $T1|cut -d: -f1`

m1=`echo $T1|cut -d: -f2`

s1=`echo $T1|cut -d: -f3`

x1=`echo "$h1*3600 + $m1*60 + $s1"|bc -l`


h2=`echo $T2|cut -d: -f1`

m2=`echo $T2|cut -d: -f2`

s2=`echo $T2|cut -d: -f3`

x2=`echo "$h2*3600 + $m2*60 + $s2"|bc -l`


if test $x1 -lt $x2

then

diff=`echo "$x2 - $x1"|bc -l`

else

diff=`echo "$x1 - $x2"|bc -l`

fi


echo "diff of Dates in seconds is $diff seconds"