Apply suggestion from @rquetiez

Co-authored-by: Romain Quetiez <romain.quetiez@combodo.com>

core/attributedef.class.inc.php

@@ -8988,12 +8988,15 @@ class AttributeStopWatch extends AttributeDefinition
 						switch ($sThresholdCode) {
 							case 'deadline':
 								if ($value) {
-									if (is_int($value)) {
+                                    if (is_numeric($value)) {
+                                        if (!is_int($value)) {
+                                            $value = intval($value);
+                                        }
 										$sDate = date(AttributeDateTime::GetInternalFormat(), $value);
 										$sRet = AttributeDeadline::FormatDeadline($sDate);
-									} else {
-										$sRet = $value;
-									}
+                                    } else {
+                                        $sRet = $value;
+                                    }
 								} else {
 									$sRet = '';
 								}

tests/php-unit-tests/unitary-tests/core/AttributeSubItemTest.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace Combodo\iTop\Test\UnitTest\Core;
+
+use AttributeDate;
+use AttributeDateTime;
+use Change;
+use Combodo\iTop\Test\UnitTest\ItopDataTestCase;
+use DateTime;
+use MetaModel;
+use UserRequest;
+
+class AttributeSubItemTest extends ItopDataTestCase
+{
+	public const CREATE_TEST_ORG = true;
+
+	/**
+	 * @param string $sAttCode
+	 * @param string $sVerb
+	 * @param string $sExpectedValue
+	 *
+	 * @return void
+	 */
+	public function testGetForTemplate()
+    {
+        $aUserRequestCustomParams = [
+            'title' => "Test DisplayStopwatch",
+        ];
+        $oUserRequest = $this->CreateUserRequest(456, $aUserRequestCustomParams);
+
+	    $iStartDate =  time() - 200;
+	    $oStopwatch = $oUserRequest->Get('ttr');
+        $oStopwatch->DefineThreshold(100, $iStartDate);
+        $oUserRequest->Set('ttr', $oStopwatch);
+
+		$sValue = $oUserRequest->Get('ttr_escalation_deadline');
+	    $oAttDef = MetaModel::GetAttributeDef(get_class($oUserRequest), 'ttr_escalation_deadline');
+		
+	    self::assertEquals('Missed by 3 min', $oAttDef->GetForTemplate($sValue, 'html', $oUserRequest));
+	    $oDateTime = new DateTime();
+	    $oDateTime->setTimestamp($iStartDate);
+	    $sDate = $oDateTime->format(AttributeDateTime::GetFormat());
+	    self::assertEquals($sDate, $oAttDef->GetForTemplate($sValue, 'label', $oUserRequest), 'label() should render the date in the format specified in the configuration file, in parameter "date_and_time_format"');
+	    self::assertEquals('Missed by 3 min', $oAttDef->GetForTemplate($sValue, 'text', $oUserRequest), 'text() should render the deadline as specified in the configuration file, in parameter "deadline_format", and depending on the user language');
+	    self::assertEquals($iStartDate, $oAttDef->GetForTemplate($sValue, '', $oUserRequest));
+    }
+}