diff --git a/packages/backend/src/models/repositories/abuse-user-report.ts b/packages/backend/src/models/repositories/abuse-user-report.ts
index 943b65eb6..144195855 100644
--- a/packages/backend/src/models/repositories/abuse-user-report.ts
+++ b/packages/backend/src/models/repositories/abuse-user-report.ts
@@ -12,7 +12,7 @@ export class AbuseUserReportRepository extends Repository<AbuseUserReport> {
 
 		return await awaitAll({
 			id: report.id,
-			createdAt: report.createdAt,
+			createdAt: report.createdAt.toISOString(),
 			comment: report.comment,
 			resolved: report.resolved,
 			reporterId: report.reporterId,
diff --git a/packages/backend/src/models/repositories/moderation-logs.ts b/packages/backend/src/models/repositories/moderation-logs.ts
index 1585d5bfc..f530613bc 100644
--- a/packages/backend/src/models/repositories/moderation-logs.ts
+++ b/packages/backend/src/models/repositories/moderation-logs.ts
@@ -12,7 +12,7 @@ export class ModerationLogRepository extends Repository<ModerationLog> {
 
 		return await awaitAll({
 			id: log.id,
-			createdAt: log.createdAt,
+			createdAt: log.createdAt.toISOString(),
 			type: log.type,
 			info: log.info,
 			userId: log.userId,
diff --git a/packages/backend/src/models/repositories/note-favorite.ts b/packages/backend/src/models/repositories/note-favorite.ts
index c5de55c0c..f4cd64e39 100644
--- a/packages/backend/src/models/repositories/note-favorite.ts
+++ b/packages/backend/src/models/repositories/note-favorite.ts
@@ -13,7 +13,7 @@ export class NoteFavoriteRepository extends Repository<NoteFavorite> {
 
 		return {
 			id: favorite.id,
-			createdAt: favorite.createdAt,
+			createdAt: favorite.createdAt.toISOString(),
 			noteId: favorite.noteId,
 			note: await Notes.pack(favorite.note || favorite.noteId, me),
 		};