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diff --git a/docs/html/xbc4.htm b/docs/html/xbc4.htm deleted file mode 100755 index f494629..0000000 --- a/docs/html/xbc4.htm +++ /dev/null @@ -1,80 +0,0 @@ -<!DOCTYPE HTML PUBLIC> -<HTML> -<TITLE>Xbase DBMS Chapter 4</TITLE> -<BODY BGCOLOR=#FFFFFF> -<H1><p align="center">Date Processing</p></H1> -<p align="center">Chapter Updated 2/12/99</p><hr> - -The objective of this chapter is to provide information regarding -the basic concepts of date arithmetic and supply generic -C/C++ date methods.<br><br> - -<h2>Leap Years</h2> - -Due to the fact that it actually takes about 365 1/4 days for -the earth to circle the sun, every fourth year and every fourth -century have an extra day added to the end of February and the year -is called a leap year. Leap years have 366 days, non leap years -have 365 days. The following code segment describes how to -determine if a given year is a leap year. - -A leap year is a year having 366 days, which can be evenly -divisible by 4 and not by 100 or divisible by 400. - -There are also leap centuries. Leap centuries are years which -are evenly divisible by 400. - -To calculate a leap year, the following code segment can be used - -<xmp> - int year; - - if(( year % 4 == 0 && year % 100 != 0 ) || year % 400 = 0 ) - LEAP_YEAR = TRUE; - else - LEAP_YEAR = FALSE -</xmp> - - -<h2>Julian Dates</h2> - -Around the time of Jesus Christ, a fellow with the name of Julias Ceasar -established the Julian calendar. The Julian calendar established every -fourth year as a leap year with 366 days and all other years having 365 days. -The months were set up the same as they are with a Gregorian calendar, which -is what we use today. A Julian date is defined as as the number of days from the -first day of the year; February 1 would have a Julian day of 32.<br><br> - -From a programmer's perspective, Julian dates are useful for doing date -arithmetic, determining the difference between two dates or calculating -a future or past date.<br><br> - -To determine the difference between two dates, convert both dates to a -Julian date and subtract one from the other.<br><br> - -To calculate a future or past date, convert the base date to a Julian date, -add (or subtract) the number of days necessary to (from) it and convert the -julian date back to a Gregorian date.<br><br> - -The Julian date routines use a base date of 01/01/0001.<br><br> - -<h2>Gregorian Dates</h2> - -In 1582, Pope Gregor XIII introduced a corrected form of the Julian calendar. -Every 4th year still has 366 days except for century years. Century years -were added as leap years if evenly divisible by 400. The year 2000 is a leap century. -<br><br> - -The methods supplied with this software are based on gregorian dates with -the format of CCYYMMDD for century, year, month and day.<br><br> - - -<h2>Date Formats</h2> - -All dates are stored in the .DBF files with format CCYYMMDD.<br><br> -All date routines work with dates formated with the same CCYYMMDD format.<br><br> - -<hr> -<p><img src="xbase.jpg"><br><hr> -</BODY> -</HTML> |