diff --git a/src/view/form/control/AphrontFormDateControlValue.php b/src/view/form/control/AphrontFormDateControlValue.php
--- a/src/view/form/control/AphrontFormDateControlValue.php
+++ b/src/view/form/control/AphrontFormDateControlValue.php
@@ -329,13 +329,16 @@
     // If this looks like an epoch timestamp, prefix it with "@" so that
     // DateTime() reads it as one. Assume small numbers are a "Ymd" digit
     // string instead of an epoch timestamp for a time in 1970.
-    if (ctype_digit($date) && ($date > 30000000)) {
-      $date = '@'.$date;
+    if ($date) {
+      if (ctype_digit($date) && ($date > 30000000)) {
+        $date = '@'.$date;
+      }
+
+      $separator = $this->getFormatSeparator();
+      $parts = preg_split('@[,./:-]@', $date);
+      return implode($separator, $parts);
     }
-
-    $separator = $this->getFormatSeparator();
-    $parts = preg_split('@[,./:-]@', $date);
-    return implode($separator, $parts);
+    return null;
   }
 
   private function getStandardTimeFormat($time) {