From: Martin Liesen <mliesen@netg.se>
Subject: RE: [delphi] Question regarding Dates
Date: Thu, 13 Jul 1995 00:43:20 +-200

As your question seams to be a general one, perhaps we should clear things
out once for all. This is what I have managed to find out about TDateTime
so far.

TDateTime is actually a floating point number defined like

TYPE	TDateTime=float;

The definition goes something like this;

The real numer of the floating point matches the days passed since 1st Jan
the year of 0001. The fraction of the floationg point matches the time of
the day, where .0 would be midnight and .5 would be noon, 0.99999... would
be just befor midnight,

Using this representation of time& dates you can easliy calculate several
things,

Days beetwen dates:
	days:=real(date1-date2);
Day of the week
	dow:=date1 div 7;
Add 25 seconds to a date/time:
	date:=date+25/(24*60*60);

There are several routines included in the SysUtils unit, giving you the
possibilty of converting & formating dates. Checkout the online manual.
A good startpoint is "TDateTime".

What you will have problem calculating is WeekNumber of date. If you would
like this function, I suspect that their is someone out there willing to
suply you with one, as it's a quite general & usefull code. Myself I use an
old routine I developed on BP7.0 using a quite simular techniqe as TDateTime.
I'll be happy to suply anyone with this library if requested.

If I were into dates below the year of 1700 I would first check out weather
Borland took in account that there were some ten missing dates, and this leap
was not introduced simultanious all across the world.   My advice, check this
out if you're not going to sticking to the latest centuries.