How do I convert the following format to unix timestamp?

Apr 15 2012 12:00AM

The format I get from DB seems to have AM at the end. I've tried using the following but it did not work:

CONVERT(DATETIME, Sales.SalesDate, 103) AS DTSALESDATE,  
CONVERT(TIMESTAMP, Sales.SalesDate, 103) AS TSSALESDATE

where Sales.SalesDate value is Apr 15 2012 12:00AM
mysql datetime timestamp unix-timestamp
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