We have recently done some (very) preliminary testing here on Windows Server 2003 64-bit, using adTempus 2.0.4 and 2.1. adTempus installs and runs fine on the win32 subsystem, and is able to run both 32-bit and 64-bit applications. So far we have not encountered any problems.

adTempus 3.0 (coming out in Autumn, tentatively) should be available in a native 64-bit version (dependent on updates to or replacements for some third-party components).