A computer clock can be wrong even when the machine is new and connected to the internet. The hardware oscillator that advances the clock is imperfect, while network synchronization only corrects it periodically. A wrong timezone, a failing real-time-clock battery, sleep behaviour, or blocked time-service traffic can make the difference more visible.
This guide separates ordinary clock drift from timezone mistakes and shows the supported ways to check synchronization on Windows, macOS, and Linux.
What clock drift means
Clock drift is the gradual difference between a device clock and a reference time scale. Consumer computers commonly use quartz oscillators. Their frequency changes slightly with temperature, manufacturing tolerance, voltage, and age. Operating systems estimate the oscillator's rate and periodically correct the clock using a network time service.
Not every wrong-looking clock is drifting. If the clock is wrong by exactly one or several whole hours, check the selected timezone and Daylight Saving Time rules first. If the date resets after the computer has been unplugged, the motherboard's real-time-clock battery may need attention.
How network synchronization helps
Network Time Protocol and related operating-system services exchange timestamps with network time servers. The client measures network delay, rejects poor samples, and adjusts or gradually steers the local clock. Internet synchronization can be very useful, but its result still depends on network conditions, server selection, and the local operating system.
A browser clock check is an independent comparison, not a replacement for the operating system's time service. The iTime.live accuracy test reports an estimated offset and a latency-based uncertainty range.
Check Windows time synchronization
- Open Settings → Time & language → Date & time.
- Confirm that the timezone is correct and that automatic time is enabled.
- Use Sync now under the additional settings section.
For diagnostics, open Command Prompt or PowerShell as an administrator and use:
w32tm /query /source
w32tm /resync
The query commands show the current source and synchronization state. Avoid unregistering the Windows Time service as a first-line fix; that is a disruptive repair step and is unnecessary for most clock problems.
Check macOS automatic time
- Open System Settings → General → Date & Time.
- Enable automatic date and time.
- Confirm that the timezone is set automatically or select the correct timezone manually.
If a managed Mac prevents changes, the setting may be controlled by an administrator. Restarting the automatic-time setting can trigger a fresh check, but repeated failure should be investigated through the network and device-management configuration.
Check Linux synchronization
On systems using systemd, the following commands report and enable network time synchronization:
timedatectl timesync-status
sudo timedatectl set-ntp true
Linux distributions may instead use chrony or another NTP implementation. Use that service's own status command and configuration rather than running two time clients against the same system clock.
When to suspect the RTC battery
The real-time clock keeps calendar time while a desktop is powered off. A depleted coin-cell battery can cause the date, BIOS settings, or hardware clock to reset after power is removed. A battery problem is different from the small drift that occurs while an operating system is running.
- Check for a date that resets after shutdown.
- Check whether firmware settings are also being lost.
- Follow the computer manufacturer's service documentation before replacing hardware.
Why correct time matters
- Authentication: Time-based one-time passwords rely on short validity windows.
- TLS certificates: A badly wrong date can make a valid certificate appear expired or not yet valid.
- Logs and file synchronization: Incorrect timestamps make event ordering and conflict resolution harder.
- Scheduling: Clock drift and timezone mistakes can both create missed meetings, but they require different fixes.
Frequently asked questions
Why is my clock wrong by exactly one hour?
A one-hour difference usually indicates a timezone or DST configuration problem rather than oscillator drift.
Does iTime.live set my computer clock?
No. A website cannot change the operating-system clock. It can only estimate the difference and point you to the supported system controls.
Is a browser comparison certified time?
No. Browser scheduling and network-path asymmetry create uncertainty. Use a properly engineered and audited timing system for regulated or safety-critical work.