How to count days for DebianReleases

== The Script ==
{{{
 #!/bin/bash
# cound_days.sh
# %s     seconds since 1970-01-01 00:00:00 UTC

echo
Bullseye=20210814
Bookworm=20230610
echo "Bullseye=$Bullseye"
echo "Bookworm=$Bookworm"
echo

S1=$(date --date="$Bullseye" +%s)
S2=$(date --date="$Bookworm" +%s)
S3=$(( 24 * 60 * 60 ))
echo "Seconds from 19700101: $S1"
echo "Seconds from 19700101: $S2"
echo "Seconds in 24 hours  : $S3"
echo

TS=$(( $S2 - $S1 ))
echo "$S2 - $S1  = $TS"
echo "Time in Seconds: $TS"
echo

TD=$(( $TS / $S3 ))
echo "$TS / $S3 = $TD"
echo "Time in Days: $TD"
echo
}}}


== The Result ==

{{{
$ ./count_days.sh 

Bullseye=20210814
Bookworm=20230610

Seconds from 19700101: 1628924400
Seconds from 19700101: 1686380400
Seconds in 24 hours  : 86400

1686380400 - 1628924400  = 57456000
Time in Seconds: 57456000

57456000 / 86400 = 665
Time in Days: 665
}}}