Re: [libreoffice-users] Can't Sum() time measurements

At 09:12 08/08/2012 -0700, Nobody Noname wrote:
> I have a list of measured times in [H]:MM:SS format and I would like 
> to sum them.  If I put in a formula:
> = B2+B3+B4+B5
> it works, but if I try:
> =Sum(B2:B5)
> I get "00:00:00" as a result.  What am I missing?

I don't know why these should be different, but what you see will 
depend crucially on cell formatting - in particular of the results cells.

At 13:01 08/08/2012 -0700, Nobody Noname wrote:
> The cells are identified as in H:MM format, but the actual 
> measurements are in minutes and seconds (with a few H:MM:SS 
> sprinkled in).  It's a bit confusing because what I see in the Cell 
> is "1:18" as in one minute and eighteen seconds, but what I see in 
> the input line is "01:18:00 AM".  The hours and minutes makes sense, 
> but what is that "AM" doing there?

That's easy: the Time formats are really not designed to represent 
time intervals (as you appear to be handling here) but times of 
day.  First, your "1:18" has been interpreted as one hour eighteen 
minutes, not one minute and eighteen seconds.  And it's then being 
(properly) identified as eight minutes past one in the morning on the 
first day of the date range (probably 30 December 1899).  If you 
select a time format instead of a date-and-time one, you will not see the date.

> If I switch to text format, I get decimal numbers (e.g. 
> 0.0541666666666667 in the "1:18" cell).

Date and time formats are actually stored as days and fraction of 
days from the time origin.  01:18 (1:18 a.m.) on the first day is 
0.054... days from the time origin.

> I suppose pursuing why those cells add like time (seconds roll over 
> to minutes at 60, etc.) when they only look like time values, but 
> don't sum() at all should be left for another day.

I think the crucial thing here is the formatting of the cell in which 
your sum appears.  Suppose you add 18:00:00 to 18:00:00.  If you 
format the result cell as Number, you will get the sum of 18 hours 
and 18 hours, namely 36 hours - which is presumably what you would 
want.  But if you format the result cell as Time, the calculation 
adds 18 hours to the first time - which, in truth, is 6 p.m. on that 
first day - which gives noon on the following day.  If you suppress 
the date element, you will see just 12:00:00, which may not be what 
you wish to see.

I trust this helps.

Brian Barker


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