System Date
Linux distros often come with a wonky system date--both in the past (i.e., when the image was generated) and in a different timezone (usually GMT). This can cause significant issues on web servers, as signed SSL certificates are only valid within a date range.
Set the timezone before trying to set the date.
Timezone
The easy-to-use tool for setting timezones is timedatectl.
timedatectl status # observe current setting timedatectl list-timezones # observe available settings timedatectl set-timezone Zone/SubZone # apply a new setting
This is just a wrapper around ln however. The manual process is:
realpath /etc/localtime # observe current setting ls /usr/share/zoneinfo # observe available zones ls /usr/share/zoneinfo/Zone # observe available subzones ln -sf /usr/share/zoneinfo/Zone/SubZone /etc/localtime # apply a new setting
Date
The system date is set using the standard date utility, run as the superuser with an argument.
sudo date 2001011230 # sets system date to January 1st, 2020 at 12:30