commit c3da1d8c433cbc6d74cc7515a6cbac4d9f7922f2
Author: Francois Marier <francois@catalyst.net.nz>
Date:   Thu Nov 5 20:41:04 2009 +1300

    lib/excellib: add write_date() function

diff --git a/lib/excellib.class.php b/lib/excellib.class.php
index ae5bcbe..69e7527 100644
--- a/lib/excellib.class.php
+++ b/lib/excellib.class.php
@@ -185,6 +185,23 @@ class MoodleExcelWorksheet {
     }
 
     /**
+     * Write one date somewhere in the worksheet
+     * @param integer $row    Zero indexed row
+     * @param integer $col    Zero indexed column
+     * @param string  $date   The date to write in UNIX timestamp format
+     * @param mixed   $format The XF format for the cell
+     */
+    function write_date($row, $col, $date, $format=null) {
+    /// Calculate the internal PEAR format
+        $format = $this->MoodleExcelFormat2PearExcelFormat($format);
+    /// Convert the date to Excel format
+        $timezone = get_user_timezone_offset();
+        $value =  ((usertime($date) + (int)($timezone * HOURSECS * 2)) / 86400) + 25569;
+    /// Add  the date safely to the PEAR Worksheet
+        $this->pear_excel_worksheet->writeNumber($row, $col, $value, $format);
+    }
+
+    /**
      * Write one formula somewhere in the worksheet
      *
      * @param integer $row    Zero indexed row