How to change ubuntu's server date and time via command line?

You can set the system date with this command:

sudo date --set="2015-09-30 10:05:59.990"

Then when using date, it should be showed correctly.

Now you should also the set hardware clock in the BIOS of the system, that the setting persists over a reboot (dureing the startup the system time is set to the value of the hardware clock). Do that with hwclock:

sudo hwclock --systohc

This gets the system clocks (sys) value and sets the hardware clock (hc). Check it with the hwclock command. Both hwclock and date should now show the same date and time.

To set your timezone, you can use this command:

sudo dpkg-reconfigure tzdata

BTW: If you use a this machine as a server, I strongly recommend using an NTP-Client to sync the time over network. So you can guarantee that all your servers have the exactly same time set. This will sync the time while the machine runs. If you have applications which are dependent of synced time over server, I recommend the NTP-Daemon. The longer it runs in the background, the more precise is the time.

1. Search for your timezone

timedatectl list-timezones

2. Set your timezone

sudo timedatectl set-timezone America/Toronto

3. Enable timesyncd

sudo timedatectl set-ntp on

With this, time should be set and synchronized.

You can see more on this tutorial : https://www.digitalocean.com/community/tutorials/how-to-set-up-time-synchronization-on-ubuntu-18-04

I dislike setting system time manually. So to fix this issue I had to combine two different answers.
To fix system time you have to use this code:

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

as given in this answer
Then you sync the hardware clock with system clock using

sudo hwclock --systohc

as given by @chaos in this thread.

Me helped:

1 - step (preparation)

 timedatectl set-local-rtc 0
 sudo timedatectl set-ntp 1
 sudo hwclock --systohc
 sudo timedatectl set-ntp 0

2 - step (set datetime)

sudo timedatectl set-time "06:24:00"
sudo timedatectl set-time "2020-04-23"
sudo hwclock --systohc

or

sudo date --set="2020-04-23 06:24:25.990"
sudo hwclock --systohc

3 - step (check datetime)

timedatectl