How can I accurately convert an INFORMIX-SE audit table column which stores UNIX timestamp[INT] into date and time?

INFORMIX-SE:

SE allows you to create an audit file for any table. The audit file has the same schema as the table being audited plus a header consisting of several columns, one of them being a_time INTEGER, which contains a UNIX timestamp of when the row was added, updated or deleted. UNIX timestamp is an INTEGER value corresponding to the number of seconds since 1970-01-01T00:00:00Z. Can anyone come up with an algorithm which can accurately convert these seconds int开发者_StackOverflow中文版o a date and time?

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Here is an algorithm that shows you how to do it: http://forums.mrplc.com/index.php?showtopic=13294&view=findpost&p=65248