diff --git a/packages/server/src/db/migrate.ts b/packages/server/src/db/migrate.ts
index c6819839..a32858b7 100644
--- a/packages/server/src/db/migrate.ts
+++ b/packages/server/src/db/migrate.ts
@@ -215,6 +215,12 @@ export function runMigrations(db: Database.Database): void {
         { name: 'federation_relay_ttl_days', type: 'INTEGER NOT NULL DEFAULT 30' },
       ]
     },
+    {
+      name: 'instance_settings',
+      columns: [
+        { name: 'default_auto_rotate_interval_days', type: 'INTEGER NOT NULL DEFAULT 90' },
+      ]
+    },
     {
       name: 'federation_peers',
       columns: [
diff --git a/packages/server/src/db/schema.ts b/packages/server/src/db/schema.ts
index 315bf70c..92d1f414 100644
--- a/packages/server/src/db/schema.ts
+++ b/packages/server/src/db/schema.ts
@@ -274,6 +274,7 @@ export const instanceSettings = sqliteTable('instance_settings', {
   maxUploadSizeBytes: integer('max_upload_size_bytes'),
   federationRelayEnabled: integer('federation_relay_enabled').notNull().default(1),
   federationRelayTtlDays: integer('federation_relay_ttl_days').notNull().default(30),
+  defaultAutoRotateIntervalDays: integer('default_auto_rotate_interval_days').notNull().default(90),
   updatedAt: integer('updated_at').notNull(),
 });
 
diff --git a/packages/server/src/routes/settings.ts b/packages/server/src/routes/settings.ts
index bb31f916..4be819b7 100644
--- a/packages/server/src/routes/settings.ts
+++ b/packages/server/src/routes/settings.ts
@@ -191,6 +191,7 @@ export async function settingsRoutes(app: FastifyInstance): Promise<void> {
       maxUploadSizeMb: Math.round(maxUploadBytes / (1024 * 1024)),
       federationRelayEnabled: row.federationRelayEnabled === 1,
       federationRelayTtlDays: row.federationRelayTtlDays,
+      defaultAutoRotateIntervalDays: row.defaultAutoRotateIntervalDays,
     };
 
     return reply.code(200).send(response);
@@ -249,6 +250,14 @@ export async function settingsRoutes(app: FastifyInstance): Promise<void> {
       updateData.federationRelayTtlDays = ttl;
     }
 
+    if (body.defaultAutoRotateIntervalDays !== undefined) {
+      const interval = Number(body.defaultAutoRotateIntervalDays);
+      if (isNaN(interval) || !Number.isInteger(interval) || interval < 1 || interval > 365) {
+        return reply.code(400).send({ error: 'defaultAutoRotateIntervalDays must be an integer between 1 and 365', statusCode: 400 });
+      }
+      updateData.defaultAutoRotateIntervalDays = interval;
+    }
+
     db.update(schema.instanceSettings).set(updateData).where(eq(schema.instanceSettings.id, 1)).run();
 
     const updatedRow = db.select().from(schema.instanceSettings).where(eq(schema.instanceSettings.id, 1)).get();
@@ -267,6 +276,7 @@ export async function settingsRoutes(app: FastifyInstance): Promise<void> {
       maxUploadSizeMb: Math.round(updatedMaxUploadBytes / (1024 * 1024)),
       federationRelayEnabled: updatedRow.federationRelayEnabled === 1,
       federationRelayTtlDays: updatedRow.federationRelayTtlDays,
+      defaultAutoRotateIntervalDays: updatedRow.defaultAutoRotateIntervalDays,
     };
 
     return reply.code(200).send(response);