Support AD and BC in year notations

Author: michel-kraemer

citeproc-java/src/main/java/de/undercouch/citeproc/csl/internal/rendering/SDatePart.java

@@ -55,7 +55,7 @@ private void renderInternal(RenderContext ctx) {
         switch (name) {
             case "year":
                 if (date.length > 0) {
-                    value = renderYear(date[0]);
+                    value = renderYear(date[0], ctx);
                 }
                 break;
 
@@ -77,7 +77,12 @@ private void renderInternal(RenderContext ctx) {
         }
     }
 
-    private String renderYear(int year) {
+    private String renderYear(int year, RenderContext ctx) {
+        if (year < 0) {
+            return (-year) + ctx.getTerm("bc");
+        } else if (year < 1000) {
+            return year + ctx.getTerm("ad");
+        }
         return String.valueOf(year);
     }
 

citeproc-java/src/test/java/de/undercouch/citeproc/FixturesTest.java

@@ -810,8 +810,9 @@ private String applyCiteprocJs(String mode, String style, ItemDataProvider itemD
             "condition_VariableNone",
             "date_Accessed",
             "date_AccessedCrash",
-            // "date_DateAD",
-            // "date_DateBC",
+            "date_DateAD",
+            "date_DateBC",
+            // we don't render error messages
             // "date_DateNoDateNoTest",
             "date_DateNoDateWithTest",
             // "date_DayOrdinalDayOneOnly",

citeproc-java/src/test/resources/fixtures/date-ad-bc-locale.yaml

@@ -0,0 +1,42 @@
+mode: bibliography
+
+style:
+  <style xmlns="http://purl.org/net/xbiblio/csl" version="1.0">
+    <locale>
+      <terms>
+        <term name="ad">AADD</term>
+        <term name="bc">BBCC</term>
+      </terms>
+    </locale>
+    <bibliography>
+      <layout>
+        <names variable="author" suffix=". ">
+          <name initialize-with=". "/>
+        </names>
+        <text variable="title"/>
+        <date form="text" variable="issued" date-parts="year-month-day" prefix=" (" suffix=")"/>
+      </layout>
+    </bibliography>
+  </style>
+
+items:
+  - id: item1
+    author:
+      - given: Given
+        family: Name
+    title: My title
+    issued:
+      date-parts:
+        - [-500]
+  - id: item2
+    author:
+      - given: Given
+        family: Name
+    title: My title
+    issued:
+      date-parts:
+        - [ 123 ]
+
+result: |
+  G. Name. My title (500BBCC)
+  G. Name. My title (123AADD)

citeproc-java/src/test/resources/fixtures/date-ad-bc.yaml

@@ -0,0 +1,36 @@
+mode: bibliography
+
+style:
+  <style xmlns="http://purl.org/net/xbiblio/csl" version="1.0">
+    <bibliography>
+      <layout>
+        <names variable="author" suffix=". ">
+          <name initialize-with=". "/>
+        </names>
+        <text variable="title"/>
+        <date form="text" variable="issued" date-parts="year-month-day" prefix=" (" suffix=")"/>
+      </layout>
+    </bibliography>
+  </style>
+
+items:
+  - id: item1
+    author:
+      - given: Given
+        family: Name
+    title: My title
+    issued:
+      date-parts:
+        - [-500]
+  - id: item2
+    author:
+      - given: Given
+        family: Name
+    title: My title
+    issued:
+      date-parts:
+        - [ 123 ]
+
+result: |
+  G. Name. My title (500BC)
+  G. Name. My title (123AD)