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create calendar date from day number 1

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simonWMC2

simonWMC2

Programmer
Aug 5, 2004
161
GB
Hello...

After a lot of help from you guys, I got a page working that converts a date into the Julian day number (day of the year - eg 01/01/06 would be day number 1, 01/02/06 would be day number 32) see (thread216-1191792)

What I want to do now is create a page that does the opposite.
The user can add a day number (eg, 32 then i want the function to work out the date - eg 01/02) There is an obvious problem with the year, as it may be a leap year. To combat this I thought of having a check box that the user wold tick if the year they were thinking of was a leap year. The function could then use a differant var of leap year days.
However, I am not sure of how to begin... can anyone help ?

thankyou
 
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ok, I got this far, but i don't really know what i am doing

function convertLydate(strLY) {
strLy = strLy;
var jd = new(strLy);
var calDte = str_dd + "/" + str_mm;
 
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Here is one I created earlier [smile]
Code: 
<html>
<head>
<title>Julian Date Sample</title>
<script type="text/javascript">
function getDateFromJulian(_data,_leap) {
	//set an array with day counts for all months
	var dayCount = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];

	// convert the number of days into a number
	var days = parseInt(_data,10);

	// some simple error checking of data
	if (days > 366 || days == 366 && !_leap) return('too many days');
	if (days < 1) return('too few days');

	// update the number of days for february if it is a leap year
	if (_leap) dayCount[1] = 29;

	var mm = temp = 0;
	if (days <= 366) {
		while (temp < days) temp += dayCount[mm++];
		temp = temp - dayCount[mm-1];
		dd = days - temp;
		return(dd + '/' + mm);
	}
}

function alertDate() {
	var _days = document.getElementById('dayinput').value;
	var _leap = document.getElementById('leap').checked;
	alert(getDateFromJulian(_days,_leap));
}
</script>
</head>
<body>
<form action="">
	<fieldset>
		<input type="text" id="dayinput"/>
		<input type="checkbox" id="leap"/><label for="leap">Leap year</label>
		<input type="button" onclick="alertDate()" value="Show date"/>
	</fieldset>
</form>
</body>
</html>
Hope this is what you are after!

Cheers,
Jeff

[tt]Jeff's Page @ Code Couch
[/tt]

What is Javascript? FAQ216-6094
 
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This function seems to work, though it does not handle the leap year.

Code: 
function ConvertDate(strDate)
{
		var number = parseInt(strDate);
		document.writeln("Data input is " + number);
		var retVal;
		
		var months = new Array(31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365);
		var marker;
		var sum = 0;
		
		for(marker = 0; marker < months.length; marker++)
		{
						
			if(number <= months[marker] )
			{
				var d = number - sum;
				var m = marker + 1;
				if(d < 10)
				{
					retVal = "0" + d;
				}
				else
				{
					retVal = "" + d;
				}
				if(m < 10)
				{
					retVal = retVal + "/0" + m;
				}
				else
				{
					retVal = retVal + "/" + m;
				}
				
				break;
			}
			
			sum = months[marker];
		}
		
		return retVal;
		
}


Let me know if that helps at all.

Nick
 
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Sorry Jeff,
Didn't see that you had already replied to this.

 
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No stress... the more different ways we see something solved, the more we learn. It's really important to remember that there are usually many ways to code a solution... and each has certain merits.

Cheers,
Jeff

[tt]Jeff's Page @ Code Couch
[/tt]

What is Javascript? FAQ216-6094
 
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Thanks Guys !!!

I have included Jeffs code in my page and it works great.

However, it would be perfect if I could have the 'result' appear in a text box ("answerLy") instead of an alert.

I guess I can do this by ammeding this function
Code: 
}
function alertDate() {
    var _days = document.getElementById('dayinput').value;
    var _leap = document.getElementById('leap').checked;
    alert(getDateFromJulian(_days,_leap));
}

but i am not sure how...

 
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that is what i thought, but it was slightly differant. But i did manage to work it out myself (woooHooo !)

I just took out the alert and added

Code: 
document.getElementById('answerly').value = getDateFromJulian(_days,_leap);

I might get the hang of this javascript thing afterall !!!!

thanks for all your help guys. I hope one day I can repay the favour !

 
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