calendar.js

一个完整的办公资源管理系统

//////////////////////////////////////////////////////////////////////
//
//  ======================================================
//  GLADIATOR JAVASCRIPT CALENDAR AND JULIAN DAY FUNCTIONS
//  ======================================================
//
//  Javascript Calendar and Julian day to Gregorian date
//  conversion functions
//
//  VERSION: 1.0.0 dated 2003.10.15
//
//  COPYRIGHT (c) 2003 by Edward H. Trager.  ALL RIGHTS RESERVED.
//  Ann Arbor, Michigan, USA.
//
//  This file and the accompanying Cascading Style Sheet file,
//  calendar.css, are released under the
//  GNU GENERAL PUBLIC LICENSE (GPL) -- see terms below.  You
//  are basically free to use and modify these files, but you
//  must preserve the copyright notice above.
//
//  AUTHOR
//  ------
//
//  Edward H. Trager  <[e-mail]>
//
//  DESCRIPTION
//  -----------
//
//  The main purpose of this file and its accompanying Cascading
//  Style Sheet, calendar.css, are to provide a Javascript popup
//  calendar for use in modern browser-based applications.
//
//  The popup calendar uses "dayOfWeek( julianDay() )" to determine
//  the day of the week of the first day of the month.
//  A complementary "julianGregorianDate()" function is also
//  provided so that you can make round-trip conversions between
//  Julian days and calendar dates if your application should
//  require it.  These functions are based directly on the
//  algorithms presented in Press et al., "Numerical Recipes in C"
//  (Cambridge University Press, 1988). The "julianGregorianDate()"
//  function is not actually required for the popup calendar
//  to work.
//
//  Unlike many other Javascript calendars that one finds on the
//  web, this calendar relies entirely on the World Wide Web
//  Consortium's (W3C) Document Object Model (DOM) and Cascading
//  Style Sheet (CSS) standards for its operation.  There is not
//  a single line of Netscape- or Internet Explorer-specific
//  code in the beast.  As a result, the code is relatively short
//  and simple, and it should work on all DOM- and CSS-compliant
//  browsers.
//
//  Also unlike many other Javascript calendars, this one will
//  happily give you a calendar for any year in the past
//  (but not preceding January 1st, 4713 BCE) or future
//  Of course you must recognize that the Gregorian calendar only
//  took effect in 1582 when Pope Gregory XIII implemented it based
//  on the recommendations of the commission headed by the Jesuit
//  mathematician and astronomer, Christoph Clavius.  At that time,
//  only the Catholic countries adopted it immediately.  Some
//  countries did not adopt it until much later.  For example, the
//  English and the American colonies did not adopt it until the
//  middle of the 18th century.  Keep this in mind if your application
//  requires historical dates!
//
//  SUMMARY OF GPL LICENSING TERMS
//  ------------------------------
//
//  This program is free software; you can redistribute it and/or
//  modify it under the terms of the GNU General Public
//  License as published by the Free Software Foundation; either
//  version 2 of the License, or (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
//  General Public License for more details.
//
//  You should have received a copy of the GNU General Public
//  License along with this software source code distribution; if not,
//  write to the Free Software Foundation, Inc., 59 Temple Place -
//  Suite 330, Boston, MA 02111-1307, USA, or review the license
//  online at:
//
//     http://www.gnu.org/licenses/gpl.txt
//
//////////////////////////////////////////////////////////////////////
//
// calendar.js
//
//////////////////////////////////////////////////////////////////////

//
// julianDay()
//
// Arguments: Y: year; M: month; D: date;
// Return: Julian day number;
//
// julianDay and julianGregorianDate algorithms adapted
// from Press et al., "Numerical Recipes in C"
// (Cambridge Univ. Press).  The Javascript adaptation
// presented here also borrows a bit from Marc A. Murison's
// Javascript implementation shown on the U.S. Naval Observatory's
// Astronomical Applications Dept. web page, "Julian Date Converter"
// at http://aa.usno.navy.mil/data/docs/JulianDate.html
//
function julianDay( Y, M, D ){

	var y,m,d;

	// Guard against arguments that are really passed as strings:
	y=parseInt(Y);
	m=parseInt(M);
	d=parseInt(D);

	var jy,ja,jm;

	// Don't permit year zero: it does not exist in the Julian calendar:
	if( y==0 ){
		alert("There was no year zero in the Julian calendar.");
		return "invalid";
	}

	// Don't permit the missing 10 days in October of 1582:
	if( y==1582 && m==10 && d>4 && d<15 ){
		alert("October 5th to 14th were skipped in October of 1582\nwhen Pope Gregory XIII implemented the calendar reforms\nof the commission headed by the Jesuit mathematician and astronomer\nChristoph Clavius.");
		return "invalid";
	}

	// Negative years represent years before the Common Era (BCE).
	// Correct for the fact that there was no year zero:
	if(y<0) y++;

	if(m>2){
		jy=y;
		jm=m+1;
	}else{
		jy=y-1;
		jm=m+13;
	}

	var julian = Math.floor( Math.floor(365.25*jy) + Math.floor(30.6001*jm) + d + 1720995 );

	// Check for the switch to the Gregorian calendar:
	var gregorianStart = 15 + 31*( 10 + 12*1582 );

	if( d + 31*(m + 12*y) >= gregorianStart ){
		ja = Math.floor(0.01*jy);
		julian += 2 - ja + Math.floor(0.25*ja);
	}

	// return the Julian day number:
	return julian;

}

//
// julianGregorianDate()
//
// Argument: Julian day number;
// Return: Julian or Gregorian date string in ISO YYYY-MM-DD form;
//
// julianDay and julianGregorianDate algorithms adapted
// from Press et al., "Numerical Recipes in C"
// (Cambridge Univ. Press).  The Javascript adaptation
// presented here also borrows a bit from Marc A. Murison's
// Javascript implementation shown on the U.S. Naval Observatory's
// Astronomical Applications Dept. web page, "Julian Date Converter"
// at http://aa.usno.navy.mil/data/docs/JulianDate.html
//
function julianGregorianDate( julian ){

	var j1, j2, j3, j4, j5;

	// This is of course the Julian day number
	// for October 15, 1582:
	var gregorianStart  = 2299161;
	if( julian >= gregorianStart ){
		var tmp = Math.floor( ( (julian - 1867216) - 0.25 ) / 36524.25 );
		j1 = julian + 1 + tmp - Math.floor(0.25*tmp);
	}else{
		j1 = julian;
	}

	j2 = j1 + 1524;
	j3 = Math.floor( 6680.0 + ( (j2 - 2439870) - 122.1 )/365.25 );
	j4 = Math.floor(j3*365.25);
	j5 = Math.floor( (j2 - j4)/30.6001 );

	var d = Math.floor(j2 - j4 - Math.floor(j5*30.6001));
	var m = Math.floor(j5 - 1);
	if( m > 12 ) m -= 12;
	var y = Math.floor(j3 - 4715);
	if( m > 2 ) y--;
	if( y <= 0 ) y--;

	return formatISODate(y,m,d);

}

//
// dayOfWeek()
//
// Argument: Julian day number;
// Return: Day of week;
//
function dayOfWeek( julian ){

	return (julian+1)%7;

}

//
// padWithZeros()
//
// Arguments: number: value to display; length: total length to display;
// Return: number padded out with zeros;
//
function padWithZeros(number,length) {
	 var str = "" + number;
	 while( str.length < length ) str = '0' + str;
	 return str;
}


//
// formatISODate()
//
// Arguments: year, month, day
// Return: Date string in ISO 8601 format for CE years.
//
//         For years BCE, the year is padded to 4 digits
//         and is prefixed with a negative sign.
//         Actual ISO 8601 conformance would require
//         expanding the padding of BCE years
//         beyond 4 digits, which I do not do, and then
//         prefixing with a negative sign.
//
//         NOTE BENE: If your application really
//         requires accurate representation of dates
//         before 1582, consider modifying this function
//         to return the Julian day number instead.  This
//         would solve the issue of BCE dates as well.
//
function formatISODate( year, month, day ){

	// Date delimiter:
	var delimiter="-";
	if(year<0){
		year= -year; year = "-" + padWithZeros(year,4);
	}else{
		year = padWithZeros(year,4);
	}
	return year + delimiter + padWithZeros(month,2) + delimiter + padWithZeros(day,2);

}

//
// setToday(): Sets objectId's value to today's ISO 8601 date string
// Arguments: Id of the target object (i.e., a text entry widget)
//
function setToday( objectId ){

	var today = new Date();
	document.getElementById( objectId ).value = formatISODate( today.getFullYear(), today.getMonth()+1, today.getDate() );

}

//