DateTime.Constructor(secondsFrom1970 as Double, timeZone as TimeZone = Nil)

From Xojo Documentation

Constructor
DateTime.Constructor(secondsFrom1970 As Double, timeZone As TimeZone)

Creates a date using number of seconds since 1 January 1970, 00:00 GMT. Use a negative value to specify a date before 1 January 1970.

Sample Code

This example creates the date April 1st, 1996 in the America/Chicago time zone:

Var d As New DateTime(828338400, New TimeZone("America/Chicago"))