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. 
