Re: TIMESTAMP and rolling time value

["Simon Coulter" <shc@xxxxxxxxxxxxxxxxx>]

"
Hello Scott,

Thanks for that.  You did understand the question correctly.  As a result of 
your successful experiment I did some research.  The VRM310 RPG IV reference 
Manual for ADDDUR states:

        "If the result field is a time field, the result must always be a 
valid Time, (if the calculated result is >= 24:00:00, subtract 24 hours or a 
multiple of 24 hours until the time is valid).  If the result is a Timestamp 
field, and the *MS or time portion is operated on, the date must be 
adjusted, each time the 24:00:00 boundary is crossed."

This statement is what I recalled.  It always struck me as counter-intuitive 
that timestamp would be treated as a compound data type and the date and 
time portions operated on seperately thus forcing the programmer to 
compensate.  I always thought that timestamp should be treated as single 
data type and rolling the microseconds should affect the time portion and 
rolling the time portion should affect the date portion.  

However, by VRM320 it appears that this anomaly has been corrected.  The 
VRM320 RPG IV Reference Manual has rewritten this section as:

        "If the result field is a time field, the result will always be a 
valid Time.  For example adding 59 minutes to 23:59:59 would give 24:58:59.  
Since this time is not valid, the compiler adjusts it to 00:58:59."

The implication here is that the RPG compiler is handling this but I would 
expect the system (as in MI) time operations to handle it.  More reading in 
the MI Reference for me.  Perhaps Barbara or Hans can comment on where the 
correction actually happens.

There is no mention of what happens to timestamp fields when the time 
duration is greater than 24 hours but the experimental evidence shows that 
the date is rolled correctly when positive or negative time durations are 
added to a timestamp data type.

There may have been something about this change in the Memo to Users for 
VRM320 but that is so old now I don't care.  It is enough to know that 
timestamp behaves the way one would expect.

Regards,
Simon Coulter.

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