Shell script date calculations


#!/bin/sh
before="$(date +%s)"
echo $before
sleep 5
Ymd="$(date '+%Y%m%d')"
echo $Ymd
after="$(date +%s)"
echo $after
elapsed_seconds="$(expr $after - $before)"
echo Elapsed time for code block: $elapsed_seconds

Date Calc using PHP

Need to calculate a date in the future or past?

$eight_days_ago = date('Ymd', mktime(0,0,0,date("m"),date("d")-8,date("Y")));