From 61dc07ef400be3613dc4fa395bca161455a402c1 Mon Sep 17 00:00:00 2001
From: Daniel Washburn <daniel@washburn.at>
Date: Wed, 4 Oct 2017 21:55:00 -0400
Subject: Initial commit of original 2014 code

---
 dst_check.xsl | 142 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 dst_check.xsl

(limited to 'dst_check.xsl')

diff --git a/dst_check.xsl b/dst_check.xsl
new file mode 100644
index 0000000..16d530b
--- /dev/null
+++ b/dst_check.xsl
@@ -0,0 +1,142 @@
+<?xml version="1.0"?>
+<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+<xsl:output method="html" encoding="UTF-8"/>
+
+<!-- DST related templates -->
+  <xsl:template name="date-to-absolute-day">
+   <xsl:param name="year"/>
+   <xsl:param name="month"/>
+   <xsl:param name="day"/>
+
+   <xsl:call-template name="julian-day-to-absolute-day">
+    <xsl:with-param name="j-day">
+     <xsl:call-template name="julian-date-to-julian-day">
+      <xsl:with-param name="year" select="$year"/>
+      <xsl:with-param name="month" select="$month"/>
+      <xsl:with-param name="day" select="$day"/>
+     </xsl:call-template>
+    </xsl:with-param>
+   </xsl:call-template>
+  </xsl:template> 
+
+  <xsl:template name="absolute-day-to-date">
+   <xsl:param name="abs-day"/>
+ 
+   <xsl:call-template name="absolute-day-to-date">
+    <xsl:with-param name="j-day">
+     <xsl:call-template name="absolute-day-to-julian-day">
+      <xsl:with-param name="abs-day" select="$abs-day"/>
+     </xsl:call-template>
+    </xsl:with-param>
+   </xsl:call-template>
+  </xsl:template> 
+
+  <xsl:template name="julian-day-to-absolute-day">
+   <xsl:param name="j-day"/>
+   <xsl:value-of select="$j-day - 1721425"/>
+  </xsl:template>
+  
+  <xsl:template name="absolute-day-to-julian-day">
+   <xsl:param name="abs-day"/>
+   <xsl:value-of select="$abs-day + 1721425"/>
+  </xsl:template> 
+
+  <xsl:template name="julian-date-to-julian-day">
+   <xsl:param name="year"/>
+   <xsl:param name="month"/>
+   <xsl:param name="day"/>
+
+   <xsl:value-of select="(1461 * ($year + 4800 + ($month - 14) div 12)) div 4 + (367 * ($month - 2 - 12 * (($month - 14) div 12))) div 12 - (3 * (($year + 4900 + ($month - 14) div 12) div 100)) div 4 + $day - 32075"/> 
+
+  </xsl:template>
+
+  <xsl:template name="last-day-of-month">
+   <xsl:param name="year"/>
+   <xsl:param name="month"/>
+   <xsl:choose>
+    <xsl:when test="$month = 2 and not($year mod 4) and ($year mod 100 or not($year mod 400))">
+     <xsl:value-of select="29"/>
+    </xsl:when>
+    <xsl:otherwise>
+     <xsl:value-of select="substring('312831303130313130313031', 2 * $month - 1,2)"/>
+    </xsl:otherwise>
+   </xsl:choose>
+  </xsl:template>
+
+  <xsl:template name="k-day-on-or-before-abs-day">
+   <xsl:param name="abs-day"/>
+   <xsl:param name="k"/>
+   <xsl:value-of select="$abs-day - (($abs-day - $k) mod 7)"/>
+  </xsl:template>
+
+  <xsl:template name="n-th-k-day">
+   <!-- The n'th occurance of k in the given month -->
+   <!-- Positive n counts from beginning of month; negative from end. -->
+   <xsl:param name="n"/>
+   <!-- k = the day of the week (0=Sun) -->
+   <xsl:param name="k"/>
+   <xsl:param name="month"/>
+   <xsl:param name="year"/>
+
+   <xsl:choose>
+    <xsl:when test="$n > 0">
+     <xsl:variable name="k-day-on-or-before">
+      <xsl:variable name="abs-day"> 
+       <xsl:call-template name="date-to-absolute-day">
+        <xsl:with-param name="year" select="$year"/>
+        <xsl:with-param name="month" select="$month"/>
+        <xsl:with-param name="day" select="7"/>
+       </xsl:call-template>
+      </xsl:variable>
+      <xsl:call-template name="k-day-on-or-before-abs-day">
+       <xsl:with-param name="abs-day" select="$abs-day"/>
+       <xsl:with-param name="k" select="$k"/>
+      </xsl:call-template>
+     </xsl:variable>
+     <xsl:value-of select="$k-day-on-or-before + 7 * ($n - 1)"/> 
+    </xsl:when>
+    <xsl:otherwise>
+     <xsl:variable name="k-day-on-or-before">
+      <xsl:variable name="abs-day">
+       <xsl:call-template name="date-to-absolute-day">
+        <xsl:with-param name="month" select="$month"/>
+        <xsl:with-param name="day">
+         <xsl:call-template name="last-day-of-month">
+          <xsl:with-param name="month" select="$month"/>
+          <xsl:with-param name="year" select="$year"/>
+         </xsl:call-template>
+        </xsl:with-param>
+        <xsl:with-param name="year" select="$year"/>
+       </xsl:call-template>
+      </xsl:variable>
+      <xsl:call-template name="k-day-on-or-before-abs-day">
+       <xsl:with-param name="abs-day" select="$abs-day"/>
+       <xsl:with-param name="k" select="$k"/>
+      </xsl:call-template>
+     </xsl:variable>
+     <xsl:value-of select="$k-day-on-or-before + 7 * ($n + 1)"/> 
+    </xsl:otherwise>
+   </xsl:choose> 
+  </xsl:template>
+
+  <xsl:template name="day-light-savings-start">
+   <xsl:param name="year"/>
+   <xsl:call-template name="n-th-k-day">
+    <xsl:with-param name="n" select="2"/>
+    <xsl:with-param name="k" select="0"/>
+    <xsl:with-param name="month" select="3"/>
+    <xsl:with-param name="year" select="$year"/>
+   </xsl:call-template>
+  </xsl:template>
+
+  <xsl:template name="day-light-savings-end">
+   <xsl:param name="year"/>
+   <xsl:call-template name="n-th-k-day">
+    <xsl:with-param name="n" select="-1"/>
+    <xsl:with-param name="k" select="0"/>
+    <xsl:with-param name="month" select="10"/>
+    <xsl:with-param name="year" select="$year"/>
+   </xsl:call-template>
+  </xsl:template>
+
+</xsl:stylesheet>
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