Your phone ignores a two-second error? How to sync your phone and PC clock to standard time

BOTH Chochim editorial team · November 5, 2026

Written as of November 5, 2026. Android details follow the Android Open Source Project (AOSP) documentation and Google Help; iPhone and Mac follow Apple Support; Windows follows Microsoft Support and Microsoft Learn; the national time server follows the Korea Research Institute of Standards and Science (KRISS). Android figures are AOSP defaults that manufacturers may change. Apple does not publish which server the iPhone uses, so we do not name one.

One minute before course registration opens, you set your phone next to your laptop and notice the seconds don't quite match. Both are set to update automatically. So which one is right? And where do these devices get the time in the first place?

The short answer: most devices ask a time server on the internet. But they ask less often than you might think, and they deliberately leave small differences alone. Here is what the official documentation actually says, and how to sync to standard time yourself.

Where does your phone get the time?

Android's design documentation lists two time sources that are on by default. One is NTP (Network Time Protocol, the standard way to ask an internet time server for the time). The other is NITZ, time information sent to phones by the mobile network's cell towers. Satellite (GNSS) time is supported but off by default.

Which one wins? Through Android 11, the cell network came first. Since Android 12, the order is reversed: the documentation says NTP is prioritized because it is "more accurate and reliable than NITZ," with NITZ as the fallback. It also notes that a tower that isn't tracking UTC correctly can supply the wrong time.

Android's default server is time.android.com, which the docs describe as an alias for Google Public NTP. The iPhone is different: Apple Support only says the date and time are set automatically based on your time zone, and does not name a server.

So is turning on automatic time all you need? This is where a surprising number comes in.

The twist: a few seconds are left alone

AOSP lists the default interval for refreshing network time: 18 hours. Android also checks after boot and when it first connects, but otherwise it asks roughly once a day, retrying at one-minute intervals if a request fails. In between, the device's own clock keeps time.

The more striking part: if the new time is within a couple of seconds of the device clock, the documentation says the clock is not changed. With the default 5-second timeout, AOSP also calculates a theoretical maximum error of about 2.5 seconds, because half the round trip is treated as uncertainty.

To be clear, that does not mean your phone is always two seconds off. It means the default design tolerates differences of that size. That is fine for daily life, but not when tickets sell out in a fraction of a second. Manufacturers can also change these defaults.

What about PCs? Windows uses time.windows.com by default. Microsoft says Windows 10 and later can reach 1-second, 50-millisecond or 1-millisecond accuracy "under the right operating conditions," but even the loosest 1-second tier requires network latency to the time source of no more than 100 ms. A home PC with default settings should not be expected to hold millisecond accuracy.

How to sync each device

First, make sure automatic time is on. Menu names vary a little by device and version.

Android, using Google's Clock app:

Open the Clock app and tap More, then Settings.
Tap "Change date and time."
Turn on "Automatic date and time."

Many devices also offer this under Settings, System, Date and time, "Set time automatically." Manufacturer screens may use different labels.

iPhone: Settings, General, Date & Time, then turn on Set Automatically. If the switch is grayed out, Apple says a Screen Time passcode or a device management profile may be the cause, and the option may not be available with every carrier or region.

Windows 11 and 10: Start, Settings, Time & language, Date & time, then turn on "Set time automatically." With administrator rights, you can also run w32tm /resync to ask for an immediate resync.

Mac: System Settings, General, Date & Time, then turn on automatic date and time. Apple's guide says you can enter "a network time server for your region" here.

So what is the right server for Korea? There is an official answer.

Who keeps Korea's standard time?

Korea's standard time is produced with atomic clocks by KRISS in Daejeon. The institute calls its realization of Coordinated Universal Time UTC(KRIS) and offers a public network time server synchronized to it. The address on its official page is ntp.kriss.re.kr.

KRISS explains how to enter this address in the Internet Time tab of the Windows Date and Time control panel, and in the Mac time server field. It also distributes its own Windows sync program.

KRISS is careful to add limits: depending on your network, errors can range from a few milliseconds to several hundred milliseconds, and the service is not intended for commercial use, industrial control or calibration. Even the national time arrives over the internet, with its delays.

That gets your device close to standard time. But does it solve the on-the-dot click? One piece is still missing.

Standard time still isn't the ticket site's time

When a booking button opens, the deciding clock is neither your phone nor the national time, but the ticket site's server clock. Servers are machines too and can drift from standard time. However precisely you set your device, the moment that counts follows that server.

So think of it in two steps: sync your device automatically or to a standard time server to remove large errors, then check how far the ticket site's server is from standard time right before you click. Chochim handles that second step by measuring the gap between the site's server and your screen.

Chochim checkpoint We don't recommend moving your clock a few seconds ahead by hand. Automatic time will put it back, and Apple advises against manual time changes made to alter app behavior. Keep your device on automatic and check the difference on screen.

FAQ

How accurate is automatic time on a phone?

Good enough for daily life. Android's default design checks about every 18 hours, leaves differences of a couple of seconds alone, and puts the theoretical maximum error at about 2.5 seconds.

Can I point Windows to Korea's standard time server?

Yes. KRISS publishes ntp.kriss.re.kr and explains how to enter it in Windows Internet Time settings. It notes errors of milliseconds to hundreds of milliseconds depending on your network.

Why is "Set Automatically" grayed out on my iPhone?

According to Apple, a Screen Time passcode or a work or school management profile can lock it, and some carriers or regions don't offer it. Update your software and check your internet connection.

In short: keep automatic time on, remember it can be a few seconds off, and for moments that matter, check against the ticket site's own server.

Check server time