diff --git a/locales/ja-JP.yml b/locales/ja-JP.yml
index 2fdab6862c..de5bc2cc3d 100644
--- a/locales/ja-JP.yml
+++ b/locales/ja-JP.yml
@@ -1312,6 +1312,7 @@ noteOfThisUser: "このユーザーのノート一覧"
 clipNoteLimitExceeded: "これ以上このクリップにノートを追加できません。"
 performance: "パフォーマンス"
 modified: "変更あり"
+modifiedAt: "変更日時"
 discard: "破棄"
 thereAreNChanges: "{n}件の変更があります"
 signinWithPasskey: "パスキーでログイン"
diff --git a/packages/frontend/src/preferences.ts b/packages/frontend/src/preferences.ts
index b32369aa11..6a03a91783 100644
--- a/packages/frontend/src/preferences.ts
+++ b/packages/frontend/src/preferences.ts
@@ -36,11 +36,12 @@ const io: StorageProvider = {
 			const cloudData = await misskeyApi('i/registry/get', {
 				scope: ['client', 'preferences', 'sync'],
 				key: syncGroup + ':' + ctx.key,
-			}) as [any, any][];
+			}) as [any, any, any][];
 			const target = cloudData.find(([scope]) => isSameScope(scope, ctx.scope));
 			if (target == null) return null;
 			return {
 				value: target[1],
+				meta: target[2],
 			};
 		} catch (err: any) {
 			if (err.code === 'NO_SUCH_KEY') { // TODO: いちいちエラーキャッチするのは面倒なのでキーが無くてもエラーにならない maybe-get のようなエンドポイントをバックエンドに実装する
@@ -52,12 +53,12 @@ const io: StorageProvider = {
 	},
 
 	cloudSet: async (ctx) => {
-		let cloudData: [any, any][] = [];
+		let cloudData: [any, any, any][] = [];
 		try {
 			cloudData = await misskeyApi('i/registry/get', {
 				scope: ['client', 'preferences', 'sync'],
 				key: syncGroup + ':' + ctx.key,
-			}) as [any, any][];
+			}) as [any, any, any][];
 		} catch (err: any) {
 			if (err.code === 'NO_SUCH_KEY') { // TODO: いちいちエラーキャッチするのは面倒なのでキーが無くてもエラーにならない maybe-get のようなエンドポイントをバックエンドに実装する
 				cloudData = [];
@@ -69,9 +70,9 @@ const io: StorageProvider = {
 		const i = cloudData.findIndex(([scope]) => isSameScope(scope, ctx.scope));
 
 		if (i === -1) {
-			cloudData.push([ctx.scope, ctx.value]);
+			cloudData.push([ctx.scope, ctx.value, ctx.meta]);
 		} else {
-			cloudData[i] = [ctx.scope, ctx.value];
+			cloudData[i] = [ctx.scope, ctx.value, ctx.meta];
 		}
 
 		await misskeyApi('i/registry/set', {
@@ -86,10 +87,10 @@ const io: StorageProvider = {
 		const fetchings = ctx.needs.map(need => io.cloudGet(need).then(res => [need.key, res] as const));
 		const cloudDatas = await Promise.all(fetchings);
 
-		const res = {} as Partial<Record<string, any>>;
+		const res = {} as Partial<Record<string, { value: any; meta: any; }>>;
 		for (const cloudData of cloudDatas) {
 			if (cloudData[1] != null) {
-				res[cloudData[0]] = cloudData[1].value;
+				res[cloudData[0]] = cloudData[1];
 			}
 		}
 
diff --git a/packages/frontend/src/preferences/manager.ts b/packages/frontend/src/preferences/manager.ts
index 438c7f6ff4..12b84706bb 100644
--- a/packages/frontend/src/preferences/manager.ts
+++ b/packages/frontend/src/preferences/manager.ts
@@ -36,7 +36,7 @@ type Scope = Partial<{
 
 type ValueMeta = Partial<{
 	sync: boolean;
-	// TODO: modifiedAtをここでも(Record個別に)持っておいた方が値の新旧比較に使えて便利そう
+	modifiedAt?: number;
 }>;
 
 type PrefRecord<K extends keyof PREF> = [scope: Scope, value: ValueOf<K>, meta: ValueMeta];
@@ -89,9 +89,9 @@ export type PossiblyNonNormalizedPreferencesProfile = Omit<PreferencesProfile, '
 export type StorageProvider = {
 	load: () => PossiblyNonNormalizedPreferencesProfile | null;
 	save: (ctx: { profile: PreferencesProfile; }) => void;
-	cloudGetBulk: <K extends keyof PREF>(ctx: { needs: { key: K; scope: Scope; }[] }) => Promise<Partial<Record<K, ValueOf<K>>>>;
-	cloudGet: <K extends keyof PREF>(ctx: { key: K; scope: Scope; }) => Promise<{ value: ValueOf<K>; } | null>;
-	cloudSet: <K extends keyof PREF>(ctx: { key: K; scope: Scope; value: ValueOf<K>; }) => Promise<void>;
+	cloudGetBulk: <K extends keyof PREF>(ctx: { needs: { key: K; scope: Scope; }[] }) => Promise<Partial<Record<K, { value: ValueOf<K>; meta: { modifiedAt: ValueMeta['modifiedAt'] }; }>>>;
+	cloudGet: <K extends keyof PREF>(ctx: { key: K; scope: Scope; }) => Promise<{ value: ValueOf<K>; meta: { modifiedAt: ValueMeta['modifiedAt'] }; } | null>;
+	cloudSet: <K extends keyof PREF>(ctx: { key: K; scope: Scope; value: ValueOf<K>; meta: { modifiedAt: ValueMeta['modifiedAt'] }; }) => Promise<void>;
 };
 
 type PreferencesDefinitionRecord<Default, T = Default extends (...args: any) => infer R ? R : Default> = {
@@ -244,13 +244,13 @@ export class PreferencesManager extends EventEmitter<PreferencesManagerEvents> {
 	}
 
 	// TODO: desync対策 cloudの値のfetchが正常に完了していない状態でcommitすると多分値が上書きされる
-	public commit<K extends keyof PREF>(key: K, value: ValueOf<K>) {
+	public commit<K extends keyof PREF>(key: K, value: ValueOf<K>): PrefRecord<K> | null {
 		const currentAccount = this.currentAccount; // TSを黙らせるため
 		const v = JSON.parse(JSON.stringify(value)); // deep copy 兼 vueのプロキシ解除
 
 		if (deepEqual(this.s[key], v)) {
 			if (_DEV_) console.log('(skip) prefer:commit', key, v);
-			return;
+			return null;
 		}
 
 		if (_DEV_) console.log('prefer:commit', key, v);
@@ -260,30 +260,39 @@ export class PreferencesManager extends EventEmitter<PreferencesManagerEvents> {
 		const record = this.getMatchedRecordOf(key);
 
 		if (parseScope(record[0]).account == null && isAccountDependentKey(key) && currentAccount != null) {
-			this.profile.preferences[key].push([makeScope({
+			const newRecord = [makeScope({
 				server: host,
 				account: currentAccount.id,
-			}), v, {}]);
+			}), v, {
+				modifiedAt: Date.now(),
+			}] as PrefRecord<K>;
+			this.profile.preferences[key].push(newRecord);
 			this.save();
-			return;
+			return newRecord;
 		}
 
 		if (parseScope(record[0]).server == null && isServerDependentKey(key)) {
-			this.profile.preferences[key].push([makeScope({
+			const newRecord = [makeScope({
 				server: host,
-			}), v, {}]);
+			}), v, {
+				modifiedAt: Date.now(),
+			}] as PrefRecord<K>;
+			this.profile.preferences[key].push(newRecord);
 			this.save();
-			return;
+			return newRecord;
 		}
 
 		record[1] = v;
+		record[2].modifiedAt = Date.now();
 		this.save();
 
 		if (record[2].sync) {
 			// awaitの必要なし
 			// TODO: リクエストを間引く
-			this.io.cloudSet({ key, scope: record[0], value: record[1] });
+			this.io.cloudSet({ key, scope: record[0], value: record[1], meta: { modifiedAt: record[2].modifiedAt } });
 		}
+
+		return record;
 	}
 
 	/**
@@ -360,8 +369,9 @@ export class PreferencesManager extends EventEmitter<PreferencesManagerEvents> {
 			if (record[2].sync && Object.hasOwn(cloudValues, key) && cloudValues[key] !== undefined) {
 				const cloudValue = cloudValues[key];
 				if (!deepEqual(cloudValue, record[1])) {
-					this.rewriteRawState(key, cloudValue);
-					record[1] = cloudValue;
+					this.rewriteRawState(key, cloudValue.value);
+					record[1] = cloudValue.value;
+					record[2].modifiedAt = cloudValue.meta.modifiedAt;
 					modified = true;
 					if (_DEV_) console.log('cloud fetched', key, cloudValue);
 				}
@@ -503,12 +513,12 @@ export class PreferencesManager extends EventEmitter<PreferencesManagerEvents> {
 			newValue = resolvedValue;
 		}
 
-		this.commit(key, newValue);
+		const commitedRecord = this.commit(key, newValue);
 
 		const done = os.waiting();
 
 		try {
-			await this.io.cloudSet({ key, scope: record[0], value: newValue });
+			await this.io.cloudSet({ key, scope: record[0], value: newValue, meta: { modifiedAt: record[2].modifiedAt } });
 		} catch (err) {
 			done();
 
@@ -607,6 +617,11 @@ export class PreferencesManager extends EventEmitter<PreferencesManagerEvents> {
 			icon: 'ti ti-cloud-cog',
 			text: i18n.ts.syncBetweenDevices,
 			ref: sync,
+		}, {
+			type: 'divider',
+		}, {
+			type: 'label',
+			text: i18n.ts.modifiedAt + ': ' + (this.getMatchedRecordOf(key)[2].modifiedAt ? new Date(this.getMatchedRecordOf(key)[2].modifiedAt!).toLocaleString() : '-'),
 		}];
 	}
 }
diff --git a/packages/i18n/src/autogen/locale.ts b/packages/i18n/src/autogen/locale.ts
index 33fdfdd1ff..7e1f3192ed 100644
--- a/packages/i18n/src/autogen/locale.ts
+++ b/packages/i18n/src/autogen/locale.ts
@@ -5260,6 +5260,10 @@ export interface Locale extends ILocale {
      * 変更あり
      */
     "modified": string;
+    /**
+     * 変更日時
+     */
+    "modifiedAt": string;
     /**
      * 破棄
      */