Crontab date setting problem

Hi, i wanted to schedule a backup script to run on 7.30pm every 1st Sat of month MAR, APR, SEP, OCT.

Am i understanding it correctly? Because it doesn't seem to run according to the schedule i needed.
[30 19 1-7 3,4,9,10 6] = (7.30pm) & (1st to 7th day of the month) & (MAR, APR, SEP, OCT) & (Sat)

 30 19 1-7 3,4,9,10 6 [ "`date +\%a`" = "Sat" ] && <script> 

does not seem to work properly also.

Thanks.

You cannot use a percent sign in a cron command line. Cron interprets it as the end of line. Quoting doesn't help either. Just put the check for saturday at the beginning of your shellscript or, if this is not possible, in a separate wrapper script.