How to set system time on Kali linux?

if you have the npt > apt-get install ntp. You must stopping or uninstalling the service doesn't help.

timedatectl set-ntp 0 (off > sync disabled)
or     
timedatectl set-ntp 1 (on > sync enabled)

Disable with timedatectl set-ntp 0 then you can change date:

date --set 1998-11-02 
date --set 21:08:00

see Maintaining Time on Debian - Datetime and NTP client and server

Method 1:

root@kali:~# timedatectl set-"time-zone"

NOTE: You can find your time-zone using timedatectl list-timezones

Method 2:

root@kali:~# timedatectl set-time "HH:MM:SS"

NOTE: 24 - Hours Time Format

TIP: Make sure to synchronize your system clock (RTC) with the hardware clock as well.

root@kali:~# hwclock -w