Date.js

I wrote these functions for my calendar/datepicker class.

Date.implement({
	minute: 60,
	hour: 3600,
	day: 86400,
	shortDayLen: 3,
	shortMonthLen: 3,
	isLeapYear: function(){ // Are we in a leap year ?
		if(this.getFullYear() % 4 == 0 && !(this.getFullYear() % 400 == 0) ? 1 : 0)
			return true;
		else return false;
	},
	days: [
		'Sunday', 'Monday', 'Tuesday','Wednesday',
		'Thursday', 'Friday', 'Saturday'
	],
	months: [
		'january','fabruary','march', 'april',
		'may','june','july','august',
		'september','october','november','december'
	],
	monthLength: function(){ // How many days in a given month ?
		var numDay = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
		if(this.isLeapYear()) numDay[1] = 29;
		return numDay[this.getMonth()];
	},
	getMonthName: function(){ // The name of the month
		return this.months[this.getMonth()];
	},
	getDayName: function(){ // The name of the day
		return this.days[this.getDay()];
	},
	format: function(how) {
		// Format a date in human language : Mercredi 20 janvier 2009
		// or american language : 01-20-2009 :) by replacing %CHAR
		//by the date's value
		
		// Shorter day name : mon 
		how = how.replace(/%a/g, this.getDayName().substr(0, this.shortDayLen));
		
		// Day name : monday
		how = how.replace(/%A/g, this.getDayName());
		
		// Number of the day in the week (1-7) : 1 = monday
		how = how.replace(/%u/g, (this.getDay() + 6) % 7 + 1);
		
		// Number of the day in the week (0-6) : 0 = sunday
		how = how.replace(/%w/g, this.getDay());

		// Shorter month name : mar 
		how = how.replace(/%b/g, this.getMonthName().substr(0, this.shortMonthLen));

		// Month name : march  
		how = how.replace(/%B/g, this.getMonthName());
		
		// Number of the month (1-12) : 3
		how = how.replace(/%m/g, this.getMonth() + 1);
		
		// Number of the month (01-12) : 03
		how = how.replace(/%zm/g, this.getMonth() + 1);
		
		// Number of the day in the month (1-31)
		how = how.replace(/%e/g, this.getDate());
		
		// Number of the day in the month (01-31)
		how = how.replace(/%d/g, this.getDate());	
		
		// Time (24 hours format, 00-23)  
		how = how.replace(/%H/g, this.getHours());
		
		// Time (12 hours format, 00-12)  
		if(this.getHours() > 12)
			H = this.getHours() - 12 + 'pm';
		else H = this.getHours() + 'am';
		how = how.replace(/%I/g, H);
		
		// Minutes
		how = how.replace(/%M/g, this.getMinutes());
		
		// Seconds
		how = how.replace(/%S/g, this.getSeconds());
		
		// Year, 2 digits (00-99) 
		year = this.getFullYear() + '';
		year = year.substr(2, 4);
		how = how.replace(/%y/g, year);
		
		// Year, 4 digits
		how = how.replace(/%Y/g, this.getFullYear());
		
		// Number of the century (year divided by 100 and rounded between 00 and 99)  
		how = how.replace(/%C/g, parseInt(this.getFullYear() / 100));
		
		
	}
});