diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -5023,6 +5023,7 @@
     'PhabricatorXHProfSampleQuery' => 'applications/xhprof/query/PhabricatorXHProfSampleQuery.php',
     'PhabricatorXHProfSampleSearchEngine' => 'applications/xhprof/query/PhabricatorXHProfSampleSearchEngine.php',
     'PhabricatorYoutubeRemarkupRule' => 'infrastructure/markup/rule/PhabricatorYoutubeRemarkupRule.php',
+    'PhabricatorZipSetupCheck' => 'applications/config/check/PhabricatorZipSetupCheck.php',
     'Phame404Response' => 'applications/phame/site/Phame404Response.php',
     'PhameBlog' => 'applications/phame/storage/PhameBlog.php',
     'PhameBlog404Controller' => 'applications/phame/controller/blog/PhameBlog404Controller.php',
@@ -11449,6 +11450,7 @@
     'PhabricatorXHProfSampleQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorXHProfSampleSearchEngine' => 'PhabricatorApplicationSearchEngine',
     'PhabricatorYoutubeRemarkupRule' => 'PhutilRemarkupRule',
+    'PhabricatorZipSetupCheck' => 'PhabricatorSetupCheck',
     'Phame404Response' => 'AphrontHTMLResponse',
     'PhameBlog' => array(
       'PhameDAO',
diff --git a/src/applications/config/check/PhabricatorZipSetupCheck.php b/src/applications/config/check/PhabricatorZipSetupCheck.php
new file mode 100644
--- /dev/null
+++ b/src/applications/config/check/PhabricatorZipSetupCheck.php
@@ -0,0 +1,29 @@
+<?php
+
+final class PhabricatorZipSetupCheck extends PhabricatorSetupCheck {
+
+  public function getDefaultGroup() {
+    return self::GROUP_OTHER;
+  }
+
+  protected function executeChecks() {
+    if (!extension_loaded('zip')) {
+      $message = pht(
+        'The PHP "zip" extension is not installed. This extension is '.
+        'required by certain data export operations, including exporting '.
+        'data to Excel.'.
+        "\n\n".
+        'To clear this setup issue, install the extension and restart your '.
+        'webserver.'.
+        "\n\n".
+        'You may safely ignore this issue if you do not plan to export '.
+        'data in Zip archives or Excel spreadsheets, or intend to install '.
+        'the extension later.');
+
+      $this->newIssue('extension.zip')
+        ->setName(pht('Missing "zip" Extension'))
+        ->setMessage($message)
+        ->addPHPExtension('zip');
+    }
+  }
+}
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldDate.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldDate.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldDate.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldDate.php
@@ -242,4 +242,8 @@
     return new ConduitEpochParameterType();
   }
 
+  protected function newExportFieldType() {
+    return new PhabricatorEpochExportField();
+  }
+
 }
diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldRemarkup.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldRemarkup.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldRemarkup.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldRemarkup.php
@@ -107,4 +107,8 @@
     return new ConduitStringParameterType();
   }
 
+  protected function newExportFieldType() {
+    return new PhabricatorStringExportField();
+  }
+
 }
diff --git a/src/infrastructure/export/field/PhabricatorEpochExportField.php b/src/infrastructure/export/field/PhabricatorEpochExportField.php
--- a/src/infrastructure/export/field/PhabricatorEpochExportField.php
+++ b/src/infrastructure/export/field/PhabricatorEpochExportField.php
@@ -6,6 +6,10 @@
   private $zone;
 
   public function getTextValue($value) {
+    if ($value === null) {
+      return '';
+    }
+
     if (!isset($this->zone)) {
       $this->zone = new DateTimeZone('UTC');
     }
@@ -21,12 +25,20 @@
   }
 
   public function getNaturalValue($value) {
+    if ($value === null) {
+      return $value;
+    }
+
     return (int)$value;
   }
 
   public function getPHPExcelValue($value) {
     $epoch = $this->getNaturalValue($value);
 
+    if ($epoch === null) {
+      return null;
+    }
+
     $seconds_per_day = phutil_units('1 day in seconds');
     $offset = ($seconds_per_day * 25569);
 
diff --git a/src/infrastructure/export/format/PhabricatorExcelExportFormat.php b/src/infrastructure/export/format/PhabricatorExcelExportFormat.php
--- a/src/infrastructure/export/format/PhabricatorExcelExportFormat.php
+++ b/src/infrastructure/export/format/PhabricatorExcelExportFormat.php
@@ -14,12 +14,23 @@
   }
 
   public function isExportFormatEnabled() {
-    // TODO: PHPExcel has a dependency on the PHP zip extension. We should test
-    // for that here, since it fatals if we don't have the ZipArchive class.
+    if (!extension_loaded('zip')) {
+      return false;
+    }
+
     return @include_once 'PHPExcel.php';
   }
 
   public function getInstallInstructions() {
+    if (!extension_loaded('zip')) {
+      return pht(<<<EOHELP
+Data can not be exported to Excel because the "zip" PHP extension is not
+installed. Consult the setup issue in the Config application for guidance on
+installing the extension.
+EOHELP
+        );
+    }
+
     return pht(<<<EOHELP
 Data can not be exported to Excel because the PHPExcel library is not
 installed. This software component is required for Phabricator to create