The symptom is confusing because the connection looks healthy. The Wi-Fi icon is full, chat apps still send messages, but the browser shows "Your connection is not private" on almost every site. In Chrome the code is often NET::ERR_CERT_DATE_INVALID. The banking app won't sign in, the app store won't download, and sometimes the clock in the corner says 2019.
This isn't a network problem. It's a time problem, and fixing it usually takes a minute.
Why a clock can cut you off
Nearly every site now uses HTTPS. When you connect, the site presents a certificate as proof of identity, and that certificate has a validity period: a start date and an end date. Certificates for large sites typically last only a few months before being replaced.
The browser has no clock of its own. It uses the device clock to check whether the certificate is still valid. If the device clock has slipped back to 2019, every certificate issued since then looks "not yet valid". If it has jumped to next year, the certificate looks "expired". Either way the browser refuses, which is exactly what it is supposed to do.
A few minutes of drift doesn't matter. The problem starts when the gap is days, months, or years. Codes from authenticator apps are fussier still: a minute or two off is enough for them to be rejected, as covered in two-step verification.
Confirming the clock is the cause
- Look at the date, not just the time. A correct time with a date a year out is easy to miss.
- Open the warning details. The browser usually says the certificate is "expired" or "not yet valid", with the dates.
- Try another device on the same Wi-Fi. If another phone opens the same site fine, the problem is this device, not the router. The wider pattern is covered in Wi-Fi problems on only one device.
Fixing it
On Android: open Settings, System, Date & time, then turn on "Set time automatically" and "Set time zone automatically". The menu path varies a little between brands, but the wording is similar.
On iPhone: Settings, General, Date & Time, turn on "Set Automatically".
On Windows: right-click the clock in the taskbar, choose "Adjust date and time", turn on "Set time automatically", then press "Sync now".
On macOS: System Settings, General, Date & Time, turn on the automatic setting.
Check the time zone too: WIB, WITA, or WIT in Indonesia. A wrong zone puts the clock out by an hour or two, which usually won't trigger certificate warnings but can throw reminders and meeting times off.
If the clock keeps going wrong
A clock that keeps drifting back has a few common causes:
| Symptom | Most likely cause |
|---|---|
| PC or laptop returns to an old date every time it starts after being unplugged | Dead CMOS battery on the motherboard |
| Phone shows the wrong time after the battery ran completely flat | Automatic time is off, or the phone hasn't reached the internet yet |
| Clock went wrong after installing a particular app | Some apps or game tricks ask for the clock to be changed manually |
| Every device on one office network is wrong | An internal time (NTP) server, or a firewall blocking it |
CMOS batteries are usually CR2032 coin cells and last several years. On a desktop PC, replacing one just means opening the case. On thin laptops it can be buried and is safer left to a repair shop.
Network equipment can be affected too. A router or CCTV recorder with the wrong time still passes internet traffic, but Wi-Fi schedules, logs, and recording timestamps become unreliable. If you use a Wi-Fi on/off schedule, check that NTP is enabled on the router.
What not to do
Don't get into the habit of pressing "Proceed to site" on certificate warnings. The same warning appears when someone is intercepting the connection, for example on a fake Wi-Fi network. Fix the clock first. If the warning remains once the clock is right, treat it as a red flag, not a minor glitch.
One reasonable exception is the Wi-Fi login page at a hotel or café, which sometimes triggers a warning before you sign in. How to handle that is in Wi-Fi login page not appearing.
Frequently asked questions
Why would a wrong clock stop websites from opening?
Sites that use HTTPS present a certificate with a start date and an expiry date. The browser checks those dates against the device clock. If the clock falls outside that window, the certificate looks either not yet valid or expired, and the page is refused.
My laptop clock goes back to an old year every time I switch it on. Why?
Almost certainly the small battery on the motherboard (the CMOS battery) has run out. It keeps the clock running while the laptop or PC is unplugged. Replacements are cheap and are usually type CR2032.
Is it safe to click "proceed anyway" on a certificate warning?
No, especially on public Wi-Fi. The same warning appears when someone is intercepting the connection. Fix the clock first; if the warning disappears once the time is right, the clock was the cause.
