[OpenISO] Problems with the "combined date and time representation"

[Norbert Bollow]

Here is some draft text for the "OpenISO.org Problem Report about OOXML"
document.

Please comment on this... do you think that this is a useful format?

(I think we shouldn't discuss all issues in this format, only those
that we expect to cause serious problems of some kind unless
appropriately addressed.)


--snip---------------------------------------------------------------

Timezone information for spreadsheet date-and-time data
=======================================================

Part 4, 3.17.4.2 and 3.17.6.7

Problem description:
~~~~~~~~~~~~~~~~~~~~

The numeric data format for date information in OOXML's spreadsheet
data format, the so-called "combined date and time representation",
has undefined semantics with regard to what timezone the date-and-time
data refers to.

Expected impact:
~~~~~~~~~~~~~~~~

Unless this issue is fixed in the specification, serious
interoperability problems are to be expected whenever date-and-time
data is communicated timezone boundaries.

In the internet age, as more and more business processes are
coordinated and integrated internationally, it is clearly a
requirement that information must remain valid when it is
communicated across timezone boundaries.



The switch to daylight-saving time and back
===========================================

Part 4, 3.17.4.3

Problem description:
~~~~~~~~~~~~~~~~~~~~

The numeric data format for date information in OOXML's spreadsheet
data format, the so-called "combined date and time representation",
represents times as fractional days, with the assumption that each
day has 24 hours.

Expected impact:
~~~~~~~~~~~~~~~~

Unless this issue is fixed in the specification, serious
interoperability problems are to be expected with regard to time data
concerning days on which the switch to daylight-saving time or back
occurs.

The interoperability problem consists in the introduction of errors
of up to one hour for each affected time value, and it is particularly
problematic because the issue can easily be overlooked during testing.



Dates before March 1, 1900
==========================

Part 3, 3.16.9
Part 4, 3.17.4.1

Problem description:
~~~~~~~~~~~~~~~~~~~~

The numeric data format for date information in OOXML's spreadsheet
data format, the so-called "combined date and time representation",
does not allow to correctly represent dates before March 1, 1900.
(Dates before January 1, 1900 cannot be preseneted at all.  Dates
from January 1, 1900 until February 28, 1900 are affected by the
so-called "leap year bug" which consists in the "combined date and
time representation" assigning a day number to the non-exiting day
"February 29, 1900" even though the year 1900 was not a leap year.
In addition, the draft standard specifies the following behavior
for the WEEKDAY function: "for dates between January 1 and February
28, WEEKDAY shall return a value for the day immediately prior to the
correct day".)

Expected impact:
~~~~~~~~~~~~~~~~

Unless this issue is fixed in the specification, serious
interoperability problems are to be expected whenever information
about dates before March 1, 1900 is exchanged by different programs.

Historical studies often consider dates before 1900.  Also, there are
people alive today who were born before 1900.  
--snap---------------------------------------------------------------


Greetings,
Norbert.


-- 
Norbert Bollow <nb at bollow.ch>                      http://Norbert.ch
President of the Swiss Internet User Group SIUG    http://SIUG.ch
Working on establishing a non-corrupt and
truly /open/ international standards organization  http://OpenISO.org