VBO bulk operations change post date

I am trying to change the post to a custom date field that was created called field_release_date. The custom field uses the “full month day year” format. I ran this script in vbo using execute php.

Before using vbo the nodes custom date field was Wednesday, December 18, 2002 this is “full month day year”
and the original post date was Monday, March 29, 2010 – 11:45pm this is the “Long” format

I then ran this script

$entity->created = $entity->field_release_date;

Results. My custom date field stayed the same Wednesday, December 18, 2002
and my post date was changed to Wednesday, December 31, 1969 – 7:00pm?
Do I need to alter the script and use $timestamp, ‘custom’

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