[ILUG] Backup script using bash, find & zip

[Justin MacCarthy]

I have a very simple bash script that everyday backs up any files modified
yesterday to a zip file. as follows

#!/bin/bash

FILENAME=`date --date=yesterday +%d_%m_%Y.ZIP`
find /d/data -daystart -mtime 1 | zip /d/backups/$FILENAME -@


However there is already is data in the /d/data directory, so I want to
modify the script to create zips for all the file that where there BEFORE I
started using this script

logic is

#get earliest mdate in the directory is [startdate]

#first zip file date is  (I can hard code this in) [firstzipdate]

#Loop from startdate to firstzipdate and create a zip for that date
#(if there are any files ) zipfilename format = dd_mm_yyyy.zip



Can anyone point me in the right direction?

Thanks
Justin