diff --git a/src/lib/features/release-plans/release-plan-milestone.ts b/src/lib/features/release-plans/release-plan-milestone.ts
index 20b6226218..fb95914d21 100644
--- a/src/lib/features/release-plans/release-plan-milestone.ts
+++ b/src/lib/features/release-plans/release-plan-milestone.ts
@@ -5,7 +5,7 @@ export interface ReleasePlanMilestone {
     name: string;
     sortOrder: number;
     releasePlanDefinitionId: string;
-    startedAt?: string;
+    startedAt?: Date;
     transitionCondition?: { intervalMinutes: number };
     strategies?: ReleasePlanMilestoneStrategy[];
     progressionExecutedAt?: string;
diff --git a/src/lib/features/release-plans/release-plan-template.ts b/src/lib/features/release-plans/release-plan-template.ts
index 4dce1dba44..65fae13b78 100644
--- a/src/lib/features/release-plans/release-plan-template.ts
+++ b/src/lib/features/release-plans/release-plan-template.ts
@@ -6,7 +6,7 @@ export interface ReleasePlanTemplate {
     name: string;
     description?: string | null;
     createdByUserId: number;
-    createdAt: string;
+    createdAt: Date;
     milestones?: ReleasePlanMilestone[];
-    archivedAt?: string;
+    archivedAt?: Date;
 }
diff --git a/src/lib/features/release-plans/release-plan.ts b/src/lib/features/release-plans/release-plan.ts
index ba314913b4..6d8a260dac 100644
--- a/src/lib/features/release-plans/release-plan.ts
+++ b/src/lib/features/release-plans/release-plan.ts
@@ -8,7 +8,7 @@ export interface ReleasePlan {
     featureName: string;
     environment: string;
     createdByUserId: number;
-    createdAt: string;
+    createdAt: Date;
     activeMilestoneId?: string;
     milestones: ReleasePlanMilestone[];
     releasePlanTemplateId: string;