Can a private employer ask for your date of birth as part of the back ground check information. Note the entire package is seen by hiring manager.

There is no law per se, for asking about a date of birth.  The law is only violated if the employer then takes some action against you because of your date of birth, which would be age discrimination if you are 40 or over.  Employers are always advised not to ask any information about a person's age because if the employee is not hired or is terminated shortly after their age is known, this strongly suggests the decision was based on age.  But if you are under the age of 40, or are still hired for the job, there would not be any discrimination or violation of law.