NIHVIVO-1610 Extracted datetime code in propStatement templates into a macro.

webapp/web/templates/freemarker/lib/lib-datetime.ftl

@@ -8,6 +8,37 @@
      but not data extraction.
  -->
 
+<#-- Macro yearInterval
+
+     Display a year interval in a property statement
+     
+     Set endYearAsRange=false to display an end year without a start year without a preceding hyphen. The hyphen indicates that
+     a range is expected but the start year is not provided (e.g., core:personInPosition); no hyphen indicates that
+     a single date is typical (e.g., core:educationalTraining).
+-->
+
+<#macro yearInterval startDateTime endDateTime endYearAsRange=true>
+    <#local yearInterval>
+        <#if startDateTime?has_content>
+            <#local startYear = xsdDateTimeToYear(startDateTime)>
+        </#if>
+        <#if endDateTime?has_content>
+            <#local endYear = xsdDateTimeToYear(endDateTime)>
+        </#if>
+        <#if startYear?? && endYear??>
+            ${startYear} - ${endYear}
+        <#elseif startYear??>
+            ${startYear} -
+        <#elseif endYear ??>
+            <#if endYearAsRange>- </#if>${endYear}
+        </#if>
+    </#local>
+    
+    <#if yearInterval?has_content>
+        <span class="listDateTime">${yearInterval}</span>
+    </#if>  
+</#macro>
+
 <#-- Function xsdDateTimeToYear 
      
      Display an XSD datetime string as a year.
@@ -18,3 +49,5 @@
 <#function xsdDateTimeToYear datetime>
     <#return datetime?date("yyyy")?string("yyyy") >
 </#function>
+
+