When using the + operator on dates multiple times the result ends up being erroneous.
Steps to Reproduce:
1. Enter =FLOOR(NOW(), "00:05") in cell A1 to have "clean" date
2. Enter =A1 + TIME(0;5;0)
3. Use the handle to apply the function multiple times
After 20 lines the output becomes:
Meaning 4 minutes have been added instead of 5
Always have the same value added on every row
User Profile Reset: No
Bug is also present when using a plain text date on first cell and formatting as a date but doesn't work with only =NOW() function in first cell.
Same behavior when using "+ (1/24/12)" as increment.
Build ID: 6.2.4-1
CPU threads: 8; OS: Linux 5.1; UI render: default; VCL: gtk3;
Locale: fr-FR (en_US.UTF-8); UI-Language: en-US
Created attachment 151762 [details]
Screenshot of the bug happening
This is a rounding issue.
date-time value have a real value in the cells:
days as integer number + hours/24 + minutes/24/60 + seconds/24/60/60
The visualization format doesn't change the cell value.
The first thing is using NOW() it gives actual date+time
So better TODAY() that gives an integer value
=ROUNDUP(TODAY()+TIME(0;5;0);7) in B1
a formula like
for the rest of the cells, rounding up with seven decimal places seems gets the right values even using seconds.
In any case not a bug, developers work hard to avoid rounding issues that comes from the floating calculations with 15 places plus sign limit, it is a hardware limitation, rounds exceeding this limits can give inaccurate results on the last places of the number.
(In reply to m.a.riosv from comment #2)
> This is a rounding issue.
yes, but there is a difference between calculation in LO 6.1 and LO 6.2.
LO 6.1 works (same with excel 2016)
Created attachment 151771 [details]
Created attachment 151772 [details]
Created attachment 151773 [details]
seems to have started with:
Use tools::Time::GetClock() in number formatter for wall clock time
Also handle rounding/scaling better in ImpGetTimeOutput() for the
 duration formats, of which [HH]:MM:SS(.0000000) is used to edit
The wall clock change made it necessary to adapt some test cases in
Test::testUserDefinedNumberFormats() where M_PI formatted to
date+time actually is 1900-01-02 03:23:53.60527 with second 53
instead of the previously rounded 54.
Reviewed-by: Eike Rathke <email@example.com>
3c35d0624c423cd4ccb08340e33de2288f03f4df is the first bad commit
Author: Norbert Thiebaud <firstname.lastname@example.org>
Date: Fri Aug 31 04:44:34 2018 -0700
:040000 040000 70cd07a8a294af840f6b5426df0f3f29798e7fa3 06198b34c24a651da6c8455cc818a145b6c23900 M instdir
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First off, the expression =FLOOR(NOW(), "00:05") is not good practice, as the second parameter to FLOOR() is expected to be a number, not a text string. Whether a string will be automatically converted to a number and if and how depends on the calculation settings under menu Tools -> Options -> Calc -> Formula, Detailed Calculation Settings; the "00:05" may result in either #VALUE! or 0 or 0.00347222222222222, the floating point value of TIME(0;5;0). A correct expression would be =FLOOR(NOW();TIME(0;5;0)), however, whether a significance of 0.00347222222222222 to FLOOR() yields an expected value is up to the reader.. the start value in A1 then is 43616.5763888889
Adding 0.00347222222222222 repeatedly in a series leads to inaccuracy due to cumulated rounding errors, this is in the nature of binary floating point representation, for which precision is not endless, and independent of any date+time formatting.
The difference between 6.2 and earlier versions is that for wall clock time format displays the underlying value is not rounded anymore into the next magnitude, same as a clock does not display 12:35 for a time of 12:34:56; you can see in your attached sample if you format the values in column A as
that starting from around A18 there's the value for example (today,now) 2019-05-31 15:34:59.99
For the expected calculation a working approach would be
and pull that down.
We maybe could do further tricks in the interpreter *iff* it is detected that for addition and subtraction operators a (date+)time operand is used and internally round to microseconds or such, but really, that only would masquerade user expectations, and then again in some circumstances the rounding might not be wanted..
Thanks for your answer, I'm now using m.a.riosv workaround.
Should I close the issue or leave it open since it may be a regression introduced in LO 6.2?
*** Bug 127143 has been marked as a duplicate of this bug. ***
Created attachment 170955 [details]
sheet to show accurate fill series are possible;
besides regression and other shortcomings ...
1048576 timestamps, 5 Minute grid, accurate to 1E-5 seconds, see attached sheet,
imho potential as a general solution for all these 'fill','downfill', 'dragfill', 'series' and similar issues ...
if i as a 'half layman' can put something like this together with 3 hours of quiet thought and trial and error ...
... i admit it was a challenging ...
but why isn't something like this standard in calc since 20 years?
the knowledge and concepts are well described since Kahan and Goldberg
and documented with rational suggestions and reasons ...
(In reply to b. from comment #12)
> imho potential as a general solution for all these 'fill','downfill',
> 'dragfill', 'series' and similar issues ...
And that is completely unrelated and thus off-topic because this bug here is not about any fill series but explicit user supplied formula expressions accumulating an error.
(In reply to Eike Rathke from comment #13)
> (In reply to b. from comment #12)
> And that is completely unrelated and thus off-topic because this bug here is
> not about any fill series but explicit user supplied formula expressions
> accumulating an error.
yes, SIR!, YES!,
but with all due respect, and i politely apologize that i have to try to clarify three things:
1. it's less the 'user defined formula' accumulating deviations, but 'fp-math' and how calc displays timestamps, in three steps:
a. the IEEE 754 double value for 5 minutes is already short by ~ 2.22222222E-19 because it's an endless fraction truncated after 53 bits,
b. this value looses it's last 24 bits (011100011100011100011100) accounting for appr. 3.2337587468900253E-12 in the addition to a value in the range of today() by crossing 24 bin ranges from -9 to +15, and that without compensation by rounding because the chopped off string starts with a '0',
c. thus the really added portion accounts for only ~ 0.0034722222189885, corresponding to a time value of ~00:04:59,9999997206 [hh:mm:ss,0000000000]
d. as calc's display for date and time values doesn't round minutes the deviation becomes visible already at very small portions and looks 'boosted' in strings formatted to show minutes but not seconds,
2. what the OP was talking about is not! his formula being erroneous, but he asks for explanation why it fails in 'dragfill' (which imho is just another interface to construct a fill series),
3. despite this situation which would also justify other proposals ... what i'd propose is! exactly that: a replacement for the user defined formula avoiding accumulation of errors (exactly it is / needs two combined formulas),
a. despite similar could - and imho should - be realized in code it also can! be used in user space as formula in sheet or similar implemented as a macro, it's an exactly targetted solution for the OP problem, imho the simpliest covering the full complexity ...
thus sorry SIR!, imho you'd shoot fast but a little bit off, please reactivate the suppressed comments.
@Alexandre Rio: 'but doesn't work with only =NOW() function in first cell.' results from 'now' mostly! not being a value with 0,00000 seconds, thus there is some 'buffer' to compensate the too small represented increment, and thus the problem will show up later after plenty additions, but will ... despite the buffer bridges to a range where the increment get's chopped before a 1 and will be rounded up, then the fail will run in the other direction ...
removing 'regression' as the change in time stamp handling is intentional,
Created attachment 171147 [details]
testsheet for 'fills' with fractional values
my proposal in c#12 was a little weak, i saw later that it has difficulties e.g. starting from 1970-01-01,
pls. find attached a new version which can handle that, it needs one special calculated correction value and then reaches ~128 bit precision in doubles (see comments and 'how and why' in the sheet,
it is 'formula based' and thus userspace (be careful trying it in macros, saw some crazy miscalculations with basic lately), but IMHO similar could / should be implemented in code to get finally rid of all these 'fill' and 'series fails',
disclaimer: 'work in progress', looks well but not yet extensively tested ... corrections welcome ...
i have experimented a bit more, and found that: ... even if you get 'exact' time values for the 5 minute intervals with tricky integer calculations, about half of them suffer 'round down' if their bitstring is truncated before a zero when added to the daily value, e.g.
~0001110001110 | 00111000 -> ~0001110001110, and the others 'round up' because of the beginning of the truncated part being '1', e.g.
~0101010101010 | 10101010 -> ~010101010101*1*,
the rounded up values are 'big enough' to bring the correct result, the rounded down values are not, the 'wall-clock-standard' makes 'just below' -> 59:59 ...?
a very very small 'protection-add' against such cases (of 1.9E-12, ~0.5 ULP in the range?) which is not harmful in the result but mixes with the 'fp-artefacts', is sufficient to save such cases ...
maybe you should think about rounding times differently, IEEE 754 provides roundup? or add a small protection-add if the result is in danger to be interpreted as time value according to wall clock standard ...
happy hacking ...
*** Bug 145131 has been marked as a duplicate of this bug. ***