On 07/08/14 17:21, Mark Rotteveel mark@...
[Firebird-general] wrote:

> What do you mean with "date.5 and date.25 I get 6pm"? Are you talking
> about doing someDate + 0.5? That works in day fractions because that is
> how the date/time arithmetic is defined (see
> https://www.ibphoenix.com/resources/documents/design/doc_185 curiously I
> wasn't able to find anything about this in the normal documentation),
> the end result however is still a time part in 100 microsecond units.
>
> Maybe I should have better qualified my previous comment: I can't
> imagine having to work with day fractions *when having to calculate an
> exact time*.

It is surprising in many projects just how much core information is not
documented.
Given the documented references to fractions in timestamp calculations
I've never had a problem with calculating exact times, in all the time
I've been using Interbase/Firebird. Since I've got data from the 1990's
Interbase days it's nice that it still does work the same :) But for the
first few years, minutes were accurate enough and 3600 was used in the
stored procedures, 86400 was a later upgrade ...

>> > I multiply the fraction by 86400 I get the number of seconds. I have
>> > material stored long before the finer resolution came about and that
>> > works fine even today. I've always worked on that basis
> As far as I know, the 100 microsecond resolution is nothing new (or at
> least has existed since Interbase 5 or earlier), however a lot of
> libraries etc don't expose it (neither does Firebird itself in some
> situations like converting to string).

It does surprise me that the 100 microsecond resolution has been around
as I'm sure I've asked the question some time in the past!

( Paul - Of cause I'm working with subtract, but I use fractional day
and time adds when building calendar information and filters for them on
the SQL it's that '(converted to seconds)' that is not on my planning )

This still leaves open the question about leap seconds and Firebird?

--
Lester Caine - G8HFL
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