System Clock in Linux

The system clock in Linux generally uses the Coordinated Universal Time (UTC) standard, as opposed to localtime.

Linux images often come with a wonky clock setting based on when the image was generated. This can cause significant issues on web servers, as signed SSL certificates are only valid within a date range.

Contents

  1. System Clock in Linux
    1. Timezone
    2. Date

Timezone

Use timedatectl(1) to set the local timezone. 

timedatectl status
timedatectl list-timezones
timedatectl set-timezone ZONE/SUBZONE

timedatectl(1) is a simple utility script; the manual equivalents roughly are... 

realpath /etc/localtime
ls /usr/share/zoneinfo/*
ln -sf /usr/share/zoneinfo/Zone/SubZone /etc/localtime   # apply a new setting

Date

Use date(1) to set the current datetime. Note that date(1) must be called by the root user to set a datetime. 

# January 1st, 2020 at 12:30
sudo date 2001011230

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