错误内容：
pi@ubuntu:~$ sudo apt update
Hit:1 http://ports.ubuntu.com/ubuntu-ports focal InRelease
Get:2 http://ports.ubuntu.com/ubuntu-ports focal-updates InRelease [114 kB]
Get:3 http://ports.ubuntu.com/ubuntu-ports focal-backports InRelease [101 kB]
Get:4 http://ports.ubuntu.com/ubuntu-ports focal-security InRelease [114 kB]
Reading package lists... Done
E: Release file for http://ports.ubuntu.com/ubuntu-ports/dists/focal-updates/InRelease is not valid yet (invalid for another 273d 3h 21min 11s). Updates for this repository will not be applied.
E: Release file for http://ports.ubuntu.com/ubuntu-ports/dists/focal-backports/InRelease is not valid yet (invalid for another 273d 3h 21min 49s). Updates for this repository will not be applied.
E: Release file for http://ports.ubuntu.com/ubuntu-ports/dists/focal-security/InRelease is not valid yet (invalid for another 273d 3h 20min 42s). Updates for this repository will not be applied.
错误原因：
原因log也提示了是因为系统时间不对，所以报错了，需要更新
sudo date -s MM/DD/YY //修改日期
sudo date -s hh:mm:ss //修改时间
修改之后就好了