Change your system date in Terminal to a date in 2018 (e.g., date 010101012018 ).

macOS High Sierra 10.13.5 update improves Mac security and stability, notably adding support for Messages in iCloud Apple Support Official Downloads from Apple

The system clock on the motherboard does not match the release date of the operating system certificate.

If you cannot find a pre-made file, create one. This guarantees no tampering.

: If you already have High Sierra 10.13.4, you can download the 10.13.5 Update directly from Apple.

It often includes a pre-configured OpenCore or Clover EFI folder suitable for popular hardware(https://ihackinOS/MacOS-Collection: All MacOS version - GitHub).

By following these steps, you should be able to successfully download and install macOS High Sierra 10.13.5 on your Mac.

In the context of macOS downloads, the extension is not an official Apple file type like DMG or ISO.

Because RDR files are specialized deployment tools, you will rarely find them on mainstream download sites. Instead, they are hosted on specific technical forums and data repositories. 1. Tech and Hackintosh Forums

Downloading OS images from third-party sources carries inherent risks. Always backup your data before attempting an installation. If possible, download the official installer from the first; only use RDR files if you have specific technical needs that the standard installer cannot meet.