OK, let's talk about time-date CTL.
Time-date CTL allows you to manage
all aspects of system time.
It's a part of system D, so it's a relatively recent
introduction.
HW clock and date are decades old,
and time-date CTL was introduced with the introduction
of system D. That's about one decade ago.
So time-date CTL status is a useful command.
It will show all time properties currently used.
Time-date CTL set time is used to change the time,
and time-date CTL set time zone is what you
can use to change the time zone.
Then there is time-date CTL set NTP,
which enables or disables NTP time synchronization.
Now, if you want to synchronize time using NTP, in general,
you need to have an NTP service.
On Red Hat, the NTP service that is used is Crony.
There's another NTP service as well,
and that is system D time sync D,
and that is not currently used on Red Hat.
That's a little bit confusing, because when
you look at the time-date CTL options,
they are closely related to system D time sync D,
but system D time sync D is not used on RHEL.
Let me show you some of the cool things
that you can do with time-date CTL.
So time-date CTL, tab, tab, is showing
all the different options.
I want time-date CTL show, which is showing me that, oh, I'm
currently in the time zone Europe-Amsterdam
on this system.
And NTP is yes, and it's synchronized,
and it's giving a little bit more information.
So how is status different?
Well, status is mainly more readable.
Hey, the thing is, the system is configured in Europe-Amsterdam,
but I happen to be on US West Coast.
So I want to change this.
And how am I going to change it?
Well, list time zones to start with.
And there I can see a lot of African,
and what I'm looking for is, I think, America-Los Angeles.
There we go, last in the list.
So I want to set it to America-Los Angeles.
How do I do that?
Well, time-date CTL set time zone, America-Los Angeles.
And now I can do my time-date CTL status again.
And there we can see that it is all changed.
So the time zone is right here.
What is also mentioned is the universal time.
Universal time is the standard time
that is the same on all computers around the world.
It's based on Greenwich main time
without daylight saving time.
And based on your time zone configuration,
the local time can be calculated, minus 7.
So local time in Los Angeles is minus 7
related to universal time.
And that is showing what is going on here.
So this is what you can do with time-date CTL.