[fpc-devel] Definition of the time-fration in a TDateTime before 30/12/1899

[Michael Van Canneyt]

On Mon, 22 May 2006, Bram Kuijvenhoven wrote:

> Michael Van Canneyt wrote:
>> The following remark in the Delphi help sheds more light on the issue:
>> 
>> "When working with negative TDateTime values, computations must handle
>> time portion separately. The fractional part reflects the fraction of
>> a 24-hour day without regard to the sign of the TDateTime value.
>> For example,
>>   6:00 am on 12/29/1899 is -1.25,
>> Not
>>   -1 + 0.25,
>> which would be -0.75. There are no TDateTime values between -1 and 0."
>
> This is really bad -- I supposed the TDateTime was a nice 'linear' mapping of 
> time (which is much nicer for all kinds of calculations).

It is, but only for dates after 1899-12-30. God only knows why Microsoft
picked this date.

Michael.