Salesforce CreatedDate and most other datetime fields comes in a GMT timezone, UTC format --> "yyyy-MM-dd'T'HH:mm:ss.SSSZ". This can be problematic when looking to perform calculations in the user timezone, especially if the date changes as a result of crossing a midnight barrier. 

Converting the field requires two steps: datevalue and date

Datevalue(date(createddate,"yyyy-MM-dd'T'HH:mm:ss.SSSZ","UTC"),"yyyy-mm-dd","PST")

Note the full datetime is required to convert into the epoch time format. Once in that format, DateValue reconverts it into a human readable and offsets the timezone.