Cause

• Type in terminal timedatectl

It should show you a terminal interface contains several dates, Local time, Universal time and RTC time,

$ timedatectl 
               Local time: Sat 2024-03-09 17:29:25 UTC
           Universal time: Sat 2024-03-09 17:29:25 UTC
                 RTC time: Sat 2024-03-09 17:29:25
                Time zone: UTC (UTC, +0000)
System clock synchronized: yes
              NTP service: n/a
          RTC in local TZ: no

you should noticed the time difference, we are in the past now. This can happen when you restore the system from a snapshot, therefore the time indication will be incorrect for at least a while.

Fix

• Install ntp using apt

sudo apt install -y ntp

• Restart the service

sudo systemctl restart ntp

• Now, check the time using timedatectl, it should be correct

• Now you can do sudo apt update with no issues.

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Sources

• Sleep Less Beastie