How timeis.au knows the time
Two separate questions, answered two different ways: which instant it is, and how to display it.
1. Where your timezone comes from
timeis.au asks your phone, not your internet connection. Your phone reports the timezone its
operating system is set to — the same setting that drives the clock on your home screen — as an
IANA zone name like Australia/Sydney.
From that one name the page works out your city and country, your GMT offset, and the daylight saving rules that apply on any date you enter — including historical dates, which matters when an incident happened either side of a DST changeover.
Why not your IP address?
Most time websites guess your location from your IP address. That breaks the moment you use a VPN — connect through another country and the site will confidently show you that country's time. It also misfires on corporate networks, mobile carriers that route traffic through another city, or on an Apple iPhone using Apple's iCloud Private Relay service.
Your device's own setting can't be fooled by a VPN, works with no lookup service, and is the same clock your phone camera stamps on a photo.
If the phone itself is set wrong
A phone left on the wrong region after travel will lie about the timezone. Tap the 🌐 globe beside the timezone line and timeis.au checks your GPS position against the timezone in use. Every zone in the timezone database has a reference city with coordinates, so the page finds the zone whose city is genuinely closest to you and compares its offset with the one being shown. If they differ, it says which zone you are nearest, how far away the zone in use is, and offers a one-tap switch. Your coordinates are used on the phone only and are never sent anywhere.
Distance matters, not just longitude: Sydney and Srednekolymsk in Russia sit on almost the same meridian but are 11,000 km apart, so a check that only compared longitudes would call that a match.
You can also tap the timezone line itself to choose any timezone in the world — sorted by city or by GMT offset, which is the quick way to find the zone next door when you are working near a border. Choosing a zone changes only how times are shown and read; it never changes the offset you calculated.
The network (IP) cross-check
If this server has the optional network-location database installed, timeis.au also compares your timezone with the one implied by your internet connection. When the two disagree and the times would actually differ, a yellow warning triangle appears beside the globe. Tap it for an explanation and a one-tap switch to the network's timezone.
This is deliberately only a hint. A VPN, a corporate network or a mobile carrier's gateway can place your connection hundreds of kilometres from where you are standing — that is exactly why timeis.au does not take its timezone from your IP address in the first place. It is a prompt to check, never an automatic change. The lookup runs on the timeis.au server against a local database, so your IP address is not sent to any third party.
2. How your phone's clock is matched to the server
Knowing the timezone doesn't help if the phone's clock is simply wrong. So timeis.au measures it against the timeis.au server, the same way time.is does:
- The page asks the server for its clock several times in a row.
- For each request it notes your phone's clock immediately before and after, and compares the server's answer against the midpoint — which cancels out about half the network delay.
- It keeps the fastest round-trip, as that one is the least distorted, and reports half of that
round-trip as the margin of error — the
±figure you see.
The result is the line at the top: “Your time is exact!”, or how far fast or slow your device is, e.g. “The difference from timeis.au was +0.031 seconds (±0.088 seconds).”
What that means for your calculations
The big clock and the NOW button both run on server-corrected time, not raw phone time. So when you capture the real time against a CCTV clock, the reading is anchored to the server — two officers with two phones drifting in opposite directions would record the same real time and calculate the same offset.
timeis.au never changes your phone's clock; a web page cannot. It measures the difference and compensates for it. The page re-checks every 15 minutes and whenever you return to it, so a long job can't drift.
If the check can't run
If the server can't be reached, the page says so rather than quietly showing unverified device time — you will always know which clock you are looking at.
3. Timezones and the offset never interfere
Every time is held internally as an absolute instant. The timezone only decides how instants are displayed and how your typed entries are read. The offset between a CCTV clock and real time is a difference between two instants, so it is identical in every timezone. If a camera sits in a different zone from where you are standing, switch zones and the displayed times change while the calculated offset does not.