Date Format Change

Hi I have a date format in a variable as Mon Jan 11 03:35:59 2010. how do i change it to YYYYMMDD format

try this

 
$ echo $ab
Mon Jan 11 03:35:59 2010
 
$ date --date "$ab" +"%Y%d%m"
20101101
 
$ mydatevar='Mon Jan 11 03:35:59 2010'
$ echo $mydatevar | date '+%Y%m%d'
date '+%Y%m%d' $mydatevar