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POHow can I convert between a Java Date and Julian day number?
 

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  1. POHow can I convert between a Java Date and Julian day number?
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    <p>How can a Java <code>Date</code> be converted into a <code>double</code> that represents a Julian day?<br> How can a Julian day number be converted into a Java <code>Date</code>?</p> <hr> <pre><code>public static double dateToJulian(Date date) { GregorianCalendar calendar = new GregorianCalendar(); calendar.setTime(date); int year; int month; float day; int a; int b; double d; double frac; frac = (calendar.get(Calendar.HOUR_OF_DAY) / 0.000024 + calendar.get(Calendar.MINUTE) / 0.001440); b = 0; year = calendar.get(Calendar.YEAR); month = calendar.get(Calendar.MONTH) + 1; DecimalFormat ceroPlaces = new DecimalFormat("0"); day = calendar.get(Calendar.DAY_OF_MONTH); day = Float.parseFloat(ceroPlaces.format(day) + "." + ceroPlaces.format(Math.round(frac))); if (month &lt; 3) { year--; month += 12; } if (FuncionSoporte.compararFechas(calendar.getTime(), calendar.getGregorianChange()) &gt; 0) { a = year / 100; b = 2 - a + a / 4; } d = Math.floor(365.25 * year) + Math.floor(30.6001 * (month + 1)) + day + 1720994.5 + b; return (d); } </code></pre> <hr> <pre><code>public static Date julianToDate(double jd) { double z, f, a, b, c, d, e, m, aux; Date date = new Date(); jd += 0.5; z = Math.floor(jd); f = jd - z; if (z &gt;= 2299161.0) { a = Math.floor((z - 1867216.25) / 36524.25); a = z + 1 + a - Math.floor(a / 4); } else { a = z; } b = a + 1524; c = Math.floor((b - 122.1) / 365.25); d = Math.floor(365.25 * c); e = Math.floor((b - d) / 30.6001); aux = b - d - Math.floor(30.6001 * e) + f; Calendar calendar = new GregorianCalendar(); calendar.setTime(date); calendar.set(Calendar.DAY_OF_MONTH, (int) aux); aux = ((aux - calendar.get(Calendar.DAY_OF_MONTH)) * 24); calendar.set(Calendar.HOUR_OF_DAY, (int) aux); calendar.set(Calendar.MINUTE, (int) ((aux - calendar.get(Calendar.HOUR_OF_DAY)) * 60)); if (e &lt; 13.5) { m = e - 1; } else { m = e - 13; } // Se le resta uno al mes por el manejo de JAVA, donde los meses empiezan en 0. calendar.set(Calendar.MONTH, (int) m - 1); if (m &gt; 2.5) { calendar.set(Calendar.YEAR, (int) (c - 4716)); } else { calendar.set(Calendar.YEAR, (int) (c - 4715)); } return calendar.getTime(); } </code></pre> <p>EDIT: Added FuncionSoporte.java code.</p> <pre><code>public class FuncionSoporte { /** * Compare 2 dates. If the first is after the second result will be positive, if the second is after then negative, 0 if they are equal. */ public static int compararFechas(Date d1, Date d2) { Calendar c1 = new GregorianCalendar(); c1.setTime(d1); Calendar c2 = new GregorianCalendar(); c2.setTime(d2); if (c1.get(Calendar.YEAR) == c2.get(Calendar.YEAR)) { if (c1.get(Calendar.MONTH) == c2.get(Calendar.MONTH)) { return c1.get(Calendar.DAY_OF_MONTH) - c2.get(Calendar.DAY_OF_MONTH); } else { return c1.get(Calendar.MONTH) - c2.get(Calendar.MONTH); } } else { return c1.get(Calendar.YEAR) - c2.get(Calendar.YEAR); } } } </code></pre>
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    1. USwill824
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      1. POHow can I convert between a Java Date and Julian day number?
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      1. POHow can I convert between a Java Date and Julian day number?
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    1. COYou should take those code snippets and post them as answers instead of in the question itself. That way users can vote on them appropriately.
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      1. POHow can I convert between a Java Date and Julian day number?
      1. USRob Hruska
    2. CO[Related](http://stackoverflow.com/questions/5651440/how-can-i-convert-between-a-java-date-and-julianday-number-dates)
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      1. USRob Hruska
    3. COA moderator closed your post. Why would you think it was appropriate to just repost it?
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