[libreoffice-users] Re: converting txt to dates

Am 24.03.2015 um 14:22 schrieb Kaj:
> Hi !
>
> Now you happened to use the wrong conversion function, VALUE instead of
> DATEVALUE, so of course it did not work. But even with the correct
> function there seems to be some issues. According to the help text for
> the date acceptance pattern: besides local ways to write date, also the
> ISO standard is supported. This standard says that dates are written,
> like all numbers in the decimal system, with most significant values to
> the left and least significant figures to the right. Hence dates are
> written "YYYY-MM-DD". I tested this in my computer and it worked very
> well. Conversely I had no success with the format DD/MM/YYYY despite I
> had introduced this as a pattern.
>
> I also tested some string manipulation to convert the string like this
> =DATEVALUE(CONCATENATE(RIGHT(A1,4),"-",MID(A1,4,2),"-",LEFT(A,2)))

and so does =VALUE(CONCATENATE(RIGHT(A1,4),"-",MID(A1,4,2),"-",LEFT(A,2)))

> and that worked fine too. However this is much the same as using the
> DATE function, proposed earlier by you Andreas:
>     =DATE(RIGHT(A1,4),MID(A1,4,2),LEFT(A1,2))
>
> BUT! wrong! The DATE function converts numbers into a date value, so you
> have to convert the strings into numbers. Thus:
>     =DATE(VALUE(RIGHT(A4,4)),VALUE(MID(A4,4,2)),VALUE(LEFT(A4,2)))

Wrong. The DATE function calculates one integer day number from 3
numbers year, month and day.
Without VALUE(), =DATE(RIGHT(A4,4),MID(A4,4,2),LEFT(A4,2)) works as well
because Calc implicitly converts integer numerals (strings consisting of
digits only).

There are no "date values" in spreadsheets. 0 formatted as date gives
1899-12-30, 36526 formatted as date gives 2000-01-01. Both values, the
"date value" and the integer are the exact same value displayed in
different number formats like you can display them in different fonts,
colors or sizes.

If the value is an integer day number without time, VALUE and DATEVALUE
return the exact same day number.

In English notation with point as decimal separator and comma as list
separator:
=VALUE("2000-1-1 12:00") => 36526.5 (full day number with time)
=DATEVALUE("2000-1-1 12:00") <=> INT(VALUE("2000-1-1 12:00")) => 36526
(integer day number only cutting of the time fraction of the day)
TIMEVALUE("3.14159") <=> MOD(VALUE("3.14159"),1) => 0.5 (the fraction of
the day cutting off the integer day number).


All this conversion from strings to numbers is unrelated to the date
acceptance patterns that determines how Calc turns your keyboard input
into day numbers.


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