📦 expo-true-time — Reliable Time Synchronization for React Native (Expo)

expo-true-time is a library designed for reliable date-time management in React Native (Expo) projects,
capable of retrieving the real time from an NTP server and maintaining estimated UTC time without network connectivity.

It works on Android using SystemClock.elapsedRealtime and is only compatible with Android devices.

🚀 Features

• ✅ Retrieves accurate UTC time from Google NTP servers (getNtpTime, getNtpTimeMS)
• ✅ After one-time NTP synchronization, estimates time without internet
• ✅ Returns UTC time in ISO format (getNtpTime, getEstimatedTimeUtc)
• ✅ Provides UTC time as timestamp (getNtpTimeMS)
• ✅ Retrieves device uptime since boot (getUpTime)
• ✅ Compatible with Expo & bare React Native

📥 Installation

# Using npm
npm install expo-true-time

# Or using yarn
yarn add expo-true-time

📄 Usage

1️⃣ Get UTC Time from NTP (ISO String)

import { getNtpTime } from "expo-true-time";

const utcString = await getNtpTime();
console.log(utcString);
// "2025-08-04T10:35:10.583Z"

2️⃣ Get UTC Timestamp (ms) and Use setBaseUtcTime

import { getNtpTimeMS, setBaseUtcTime } from "expo-true-time";

const ntpTimestamp = await getNtpTimeMS(); // timestamp (ms)
await setBaseUtcTime(ntpTimestamp); // set as base UTC time

⚠️ Important: setBaseUtcTime should be provided a timestamp (ms), not an ISO string.

3️⃣ Get Estimated UTC Time

import { getEstimatedTimeUtc } from "expo-true-time";

const estimatedUtc = await getEstimatedTimeUtc();
console.log(estimatedUtc);
// "2025-08-04T10:35:10.583Z"

4️⃣ Get Device Uptime

import { getUpTime } from "expo-true-time";

const upTimeMs = await getUpTime();
console.log(upTimeMs);
// E.g., 3600000 (1 hour in milliseconds)

⚡ Includes time while the device was awake and asleep.
⚡ Not affected by system clock changes.
⚡ Returns a Long (ms) value.

⚙️ API Reference

| Method | Description | Parameter | Return Type | | ---------------------------- | ------------------------------------------------------------- | ------------ | ----------------------------------- | ----- | | getNtpTime() | Retrieves UTC time from Google NTP servers (ISO string) | None | string "YYYY-MM-DDTHH:mm:ss.sssZ" | | getNtpTimeMS() | Retrieves UTC time as timestamp (ms) from Google NTP servers | None | number (ms) | | setBaseUtcTime(ms: number) | Sets a base UTC timestamp for calculating estimated UTC time | ms: number | void | | getEstimatedTimeUtc() | Returns the estimated UTC time in ISO format | None | string | null | | getUpTime() | Returns the device uptime since boot (includes awake + sleep) | None | number (ms) |

📌 Notes

• ⚠️ Android devices only.
• Internet is required initially for NTP synchronization.
  • Alternatively, you can provide a trusted source's UTC timestamp (ms) to setBaseUtcTime.
  • Afterwards, getEstimatedTimeUtc() can provide estimated UTC time without network.
• After getNtpTimeMS() is stored via setBaseUtcTime, estimated time works offline.
• The library does not handle timezone conversions; it only returns UTC time.

📜 License

MIT © 2025 — Emre Dönmez & Contributors