diff --git a/ui/src/Stores/SilenceFormStore.js b/ui/src/Stores/SilenceFormStore.js
index 6d31b3a06..c7090a515 100644
--- a/ui/src/Stores/SilenceFormStore.js
+++ b/ui/src/Stores/SilenceFormStore.js
@@ -138,12 +138,11 @@ class SilenceFormStore {
 
       incDuration(minutes) {
         this.endsAt = moment(this.endsAt).add(minutes, "minutes");
+        this.verifyStarEnd();
       },
       decDuration(minutes) {
-        const newEndsAt = moment(this.endsAt).subtract(minutes, "minutes");
-        if (newEndsAt.isAfter(this.startsAt)) {
-          this.endsAt = newEndsAt;
-        }
+        this.endsAt = moment(this.endsAt).subtract(minutes, "minutes");
+        this.verifyStarEnd();
       },
 
       get toAlertmanagerPayload() {
@@ -163,7 +162,7 @@ class SilenceFormStore {
             .millisecond(0)
             .toISOString(),
           endsAt: this.endsAt
-            .second(59)
+            .second(0)
             .millisecond(0)
             .toISOString(),
           createdBy: this.author,