diff --git a/api/Utils/PrayerTimesHelper.php b/api/Utils/PrayerTimesHelper.php
index 53274e9..a06b542 100644
--- a/api/Utils/PrayerTimesHelper.php
+++ b/api/Utils/PrayerTimesHelper.php
@@ -314,7 +314,11 @@ private static function calculateTimings(DateTime $d, PrayerTimes $pt, ?array $t
         $pt = self::applyMethodSpecificTuning($pt, $tune, $d, $adjustment, $methodSettings);
         $timings = $pt->getTimes($d, $latitude, $longitude, null, $latitudeAdjustmentMethod, $midnightMode, $timeFormat);
 
-        return Timezone::addTimezoneAbbreviation($timings, $d);
+        if ($timeFormat !== PrayerTimes::TIME_FORMAT_ISO8601) {
+            return Timezone::addTimezoneAbbreviation($timings, $d);
+        }
+
+        return $timings;
     }
 
 }