Recipe 4.6. Working with the Julian Calendar

Problem

You need to work in the old Julian system of dates.

Solution

<xsl:template name="ckbk:julian-date-to-julian-day">
    <xsl:param name="year"/>
    <xsl:param name="month"/>
    <xsl:param name="day"/>
   
    <xsl:variable name="a" select="floor((14 - $month) div 12)"/>
    <xsl:variable name="y" select="$year + 4800 - $a"/>
    <xsl:variable name="m" select="$month + 12 * $a - 3"/>
   
    <xsl:value-of 
        select="$day + floor((153 * $m + 2) div 5) + 365 * $y 
        + floor($y div 4) - 32083"/>
   
  </xsl:template>

Once you have the Julian day, you can use other recipes in this chapter for date formatting, date math, or conversion to other calendar systems.

Discussion

The Julian system is rarely used in modern times. (One exception is the Russian Orthodox Church.) The Julian calendar was abandoned in favor of the Gregorian calendar due to its slightly inaccurate estimate of a year containing 365 1/4 days. The mean length is actually 365.2425 days, and over time, the seasons began to shift under the Julian system.