Macintosh Operating System or macOS (previously Mac OS X and later OS X) is officially an Apple operating system designed for Mac computers. It is based on the Unix operating system. The coding scheme is based upon technologies developed between 1985 and 1997 at NeXT, a company that was created by the Co-founder of Apple, Steve Jobs.

macOS Inteface

When the user is trying to reinstall macOS or macOS Sierra, he/she may be encountered with an error as follows:

Error Notification


After brainstorming user’s feedback in the online community, it has been identified that the main reason for this error is the incorrect system date setting. Now, this can happen if the user hasn’t used his/her Mac for a while or accidentally changed settings for date and time.

Method 1: Changing system date and time from Mac Settings

Use this method only if you still have access to old macOS installed. Otherwise, go for the second method. Follow these steps:

  1. Choose Apple menu and click System Preferences.
    Navigating to System Preferences
  2. Click Date & Time.
    You may need to click the lock icon and then enter an administrator name and password.
  3. Click Date & Time and set the date & time manually.
  4. Deselect Set date and time automatically and set today’s date on the calendar.
    Setting date & time manually
  5. Keep dragging the clock’s needles until it shows the correct time, then click Save.

Now try reinstalling the macOS again, the error should be fixed now.

Method 2: Changing system date from Terminal

Use this method only if you no longer have access to old macOS installed, as mentioned previously. Follow these steps:

  1. Go to Utilities and click Terminal.
    Opening Terminal from macOS Utilities
  2. Type the following command and hit Enter.

    This command will result in the display of date to which the system currently has been set to. It might be reset to 2001 for some arbitrary reason, therefore, we need to set it to the right date.

  3. To do this, type the following command and hit Enter.
    date -u [month][day][hour][minute][year]

    Two-digit numbers based on UTC should be replaced with every bracket. You can see below, how the command should look like according to your current time and date – October 30th, 2019 01:15. UTC is used instead of other timezones to avoid trouble. Just enter it exactly like this:

    date -u 1030011519
  4. Check the set date and time by running the first command again. The error should be fixed now.
Kevin Arrows
Kevin is a dynamic and self-motivated information technology professional, with a Thorough knowledge of all facets pertaining to network infrastructure design, implementation and administration. Superior record of delivering simultaneous large-scale mission critical projects on time and under budget.
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