Today (while migrating the userdata for dracoblue.net) I was facing the issue, that I needed to transform the unix timestmaps (used by SimpleMachinesForum) into date-objects.
After trying different things, I noticed that the easiest way is the java-function to create a new Date-Object.
Converting UnixTimestamp (int/long) to Date:
new java.sql.Timestamp(new Long(row1.registerDate)*1000)
Explanation: Since the Timestamp expects milliseconds since 01/01/1970, but I have seconds, I need to multiply be 1000. But since the initial Value may be a int, which can't be that big we need to convert it to Long first.
Converting Date String (e.g. dd.MM.yyyy) to UnixTimestamp:
Converting Date Object to UnixTimestamp: