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Thread: Getting date based on days past year

  1. #1
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    Default Getting date based on days past year

    Ok, I would assume someone out there has this already done, or atleast something similar that I can change.

    I'm given a number representing the number of days past January 1, 1900. I need to calculate the date the number represents. This is not for a school assignment or anything, I actually need this for a program I'm writing. It wouldnt be that bad, except I need to take into account of the differing number of days in a month and the leap years.

    My goal for this is to be able to get the Month and the Year. I dont care about the day of the month.

    If anyone has this already done or want to take a crack at it, I would be appreciative.
    Last edited by aussiemcgr; July 14th, 2010 at 03:13 PM. Reason: More Information


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    Default Re: Getting date based on days past year

    Take a look at Calendar in the java API. It will allow you to set a date, and from there you can add on specified times and recalculate the date.A simple example:
    public static void main(String[] args){
    		SimpleDateFormat sdf = new SimpleDateFormat("yyyy,MM,dd");
    		Calendar cal = sdf.getCalendar();
    		cal.set(2010, Calendar.JULY, 14);
    		Date date = cal.getTime();
    		System.out.println(sdf.format(date));
    		for ( int i = 0; i < 30; i++ ){
    			cal.add(Calendar.HOUR, 24);
    		}
    		date = cal.getTime();
    		System.out.println(sdf.format(date));
    }

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    Default Re: Getting date based on days past year

    Ok, I was having a look at it.

    So tell me if I'm correct:
    Calendar cal = sdf.getCalendar();
    cal.set(2010, Calendar.JULY, 14);
    This sets the date selection to do calculations from.


    for ( int i = 0; i < 30; i++ )
    {
                cal.add(Calendar.HOUR, 24);
    }
    This moves the selection over 30 days.


    And really thats the only relevant stuff for me right?

    So instead of incrementing 30 days, if I wanted to increment 38353 days from Jan-1-1990, I would say:
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy,MM,dd");
    Calendar cal = sdf.getCalendar();
    cal.set(1990, Calendar.JANUARY, 1);
    for ( int i = 0; i < 38353; i++ )
    {
                cal.add(Calendar.HOUR, 24);
    }

    Am I correct?

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    Default Re: Getting date based on days past year

    Pretty much...its not extremely elegant but it works. I've never verified this method for leap years and such, so you may want to verify this with a short test.

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