File: jquery.date.js

/*------------------------------------------------------------------------
// This plugin contains some functions for manipulating dates
//
// 27/09/2013 - Sandro Alves Peres
// http://www.zend.com/en/yellow-pages#show-ClientCandidateID=ZEND022656
//-----------------------------------------------------------------------*/

(function($){
  

    $.isLeapYear = function( year )
    {
        if( (year % 4) == 0 && ((year % 100) != 0 || (year % 400) == 0) )
        {
            return true;
        }
        else
        {
            return false;	
        }
    };


    $.isDate = function( date ) // dd/mm/yyyy
    {
        if( !/^\d{2}\/\d{2}\/\d{4}$/.test( date ) )
        {
            return false;
        }    

        var arrDate   = date.split("/");
        var daysMonth = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];

        var day   = parseInt(arrDate[0], 10);
        var month = parseInt(arrDate[1], 10);
        var year  = parseInt(arrDate[2], 10);		 

        if( $.isLeapYear( year ) )
        {
            daysMonth[1] = 29; // February in Leap Year
        }

        if( year > 0 )
        {
            if( month > 0 && month <= 12 )
            {
                if( day > 0 && day <= daysMonth[ month-1 ] )
                {
                    return true;
                }
                else
                {
                    return false;  
                }
            }
            else
            {
                return false;
            }
        }
        else
        {
            return false;
        }	  
    };
    
    
    $.daysOfMonth = function( month, year )
    {
        if( month < 8 && (month % 2) == 1 || month > 7 && (month % 2) == 0 )
        {
            return 31;
        }
        
        if( month != 2 )
        {
            return 30; 
        }
        
        if( $.isLeapYear(year) )
        {
            return 29;
        }
        
        return 28;
    },    
    
    
    $.addDays = function( date, days ) // days might be negative
    {
        var arrDate = date.split("/");
        var month   = parseInt(arrDate[1], 10);
        var year    = parseInt(arrDate[2], 10);

        if( days >= 0 )
        {
            var day = parseInt(arrDate[0], 10);
            day += days;

            while( day > $.daysOfMonth(month, year) )
            {
                day -= $.daysOfMonth(month, year);
                month++; 

                if( month > 12 )
                {
                    month = 1;
                    year++;
                }
            }
        }
        else
        {
            var day = parseInt(arrDate[0], 10);
            
            for( var i=0; i < (days * -1); i++ )
            {
                if( day > 1 )
                {
                    day--;
                }
                else
                {
                    if( month > 1 )
                    {
                        month--;
                    }
                    else
                    {
                        month = 12;
                        year--;
                    }
                    
                    day = $.daysOfMonth(month, year);
                }
            }							
        }

        for( var i=1; i <= 4; i++ )
        {
            day   = '0' + day;
            month = '0' + month;
            year  = '0' + year;
        }
        
        day   = day.slice(-2);
        month = month.slice(-2);
        year  = year.slice(-4);        

        return day.concat("/", month, "/", year);
    },
    
    
    $.toDays = function( date ) // format dd/mm/yyyy
    { 
        var days      = 0, days29 = 0;  
        var date      = date.split("/");
        var daysMonth = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];

        date[0] = parseInt(date[0], 10);
        date[1] = parseInt(date[1], 10);
        date[2] = parseInt(date[2], 10);

        for(var i=1; i < date[2]; i++)
        {
            if( $.isLeapYear(i) )
            {
                days29++;
            }	  	
        }

        if( $.isLeapYear(date[2]) )
        {
            if( date[1] > 2 || (date[1] == 2 && date[0] == 29) )
            {
                daysMonth[1] = 29;
            }
        }

        for( var i=0; i <= (date[1] - 2); i++ )
        {
            days += daysMonth[i];
        }

        days += ((date[2] * 365) + date[0] + days29);
        
        return days;
    };


    $.datediff = function( dateStart, dateEnd )
    { 
        return ($.toDays(dateEnd) - $.toDays(dateStart));
    };
    
    
})(jQuery);