How to manipulate date keeping the same time via command line

This is an example of what ( I think ) you want. It will change the year only to last year for 4 minutes then back to current date again. Your machine needs to be connected to the Internet for this to work:

sudo bash -c "timedatectl set-ntp off && date -s 'last year' && sleep 4m && timedatectl set-ntp on"

For the below to work, you should first go to Settings → Date & Time and disable Automatic Date & Time.

You can then use the following command as a (long) one-liner:

sudo date --set="2010-05-02 $(date '+%T')" && sleep 10 && sudo date -s "$(wget -qSO- --max-redirect=0 google.com 2>&1 | grep Date: | cut -d' ' -f5-8)Z"

The above command:

• Gets the current system time:

  date '+%T'
  

  and sets the date to the one you wish, keeping the current time:

  sudo date --set="2010-05-02 $(date '+%T')"
  

  In this example the date, which you may change to what you need, is 2010-05-02.

• Keeps the altered date for the specified time interval using the sleep command. Here I have used sleep 10 to keep the altered time for 10 seconds. You can add an m, h, or d suffix to sleep's argument (here 10) to specify the time in minutes, hours, or days, respectively.

• Reverts the time to the current time (requires internet access):

  sudo date -s "$(wget -qSO- --max-redirect=0 google.com 2>&1 | grep Date: | cut -d' ' -f5-8)Z"
  

  Credits to Shrukul Habib.