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>Are you sure the collating sequence on that tag is Machine? Other collating sequences, when used on stuff other than strings, may yield gray hair, higher blood pressure and neurological disorders.
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Collate is set to MACHINE...for sure :)

>Internally, the datetime is two integers - one for the Julian day number, and the other for the number of milliseconds. There should be no rounding issues here; if you add 1, it should add a thousand milliseconds to the right portion of it, period. I would really be surprised if adding 1 to a datetime ever managed to produce a duplicate.
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It adds a second (or, i suppose it adds 1,000 milliseconds...not a millisecond) every time you add 1 to the dateTime. It does not produce duplicates, as far as comparing adjacent values in the memory variable. However, VFP stores the information in the table in such a way that it *thinks* it IS a duplicate (as far as index uniqueness goes), when in reality it is NOT a duplicate. As Jonathan stated yesterday, you can pull the fields from adjacent duplicate records out to variables, and the 2 variables will compare as *not* equal (but visually appear to be equal). Sounds like rounding issue to me...