This applies if the installer shows one of these messages (and you did not get the prohibitory symbol at boot, meaning the version is compatible with your Mac):

• “This copy of the Install macOS… application is damaged, and can’t be used to install macOS”
• “No packages were eligible for install”
• “This copy of the Install OS X… application can’t be verified”
• “The installer payload failed signature check”

The cause is the installer’s digital signature: its certificate isn’t valid on the date the Mac’s clock shows. Either the installer is a copy from before October 24, 2019 (when Apple’s certificate expired), or the clock is in the past.

Boot from the USB stick or Recovery and open Utilities → Terminal, without leaving the installer.

Installer Terminal

If it shows 2000 or 2001, the clock (PRAM) battery is dead: set today’s date (example for Oct 24, 2026 at 12:00) and try again. That’s all you need if your installer is a fresh copy.

Format MMDDhhmmYY — use today’s real date

Apple re-signed its installers with a certificate valid until 2029. From the official previous-versions page: High Sierra through Sequoia via the App Store; Sierra, El Capitan, Yosemite, Mountain Lion and Lion as a .dmg. With this copy, don’t change the date: leave it at today.

On a Mac running Catalina or later — list the installers Apple offers Download one (change the number to the version you want)

If the .pkg inside the .dmg refuses to install because your current Mac is newer, do it from a Mac that supports that version.

A USB stick made from an old installer keeps the expired certificate: you have to create it again. 16 GB or larger, formatted as Mac OS Extended (Journaled) and named MyVolume. Everything on it is erased.

High Sierra, Mojave, Catalina and later (change the app name) Sierra El Capitan

Only for copies older than October 2019 (or versions Apple no longer offers, such as Mavericks). The date must fall after the installer was signed and before Oct 24, 2019.

1. Disconnect Wi-Fi and the network cable.
2. Open Utilities → Terminal from the installer.
3. Type your version’s date (table below).
4. Quit via Terminal → Quit Terminal (closing the window isn’t enough) and install again.
5. If it doesn’t work, try the “Alternative” column or move the year up by one.

High Sierra example — Jan 1, 2018, 01:01

On Intel Macs, reset NVRAM: at power-on hold Option + Command + P + R for about 20 seconds. If the clock goes back to 2001 after shutting down, replace the PRAM battery.

Connect to the internet and enable System Preferences → Date & Time → Set automatically. A fake date breaks secure browsing and Time Machine timestamps.

Terminal alternative (Mojave and later) High Sierra and earlier