Learn to find and set system date and time at the Linux command line.
Linux date command summary with examples (3:40)
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The Command and Why You Need It
Our fifteenth word, or command to memorize is date from the category System.
date allows you to display or set the
system time and date.
Recall from our last video (tutorial) we talked about answering
questions, and the date will help us
answer the when question.
Before we start, it helps to think of commands as mini programs and
most follow this structure:
command -option(s) argument(s).
The date command has
10 options and the most common argument is a
date/time format which can be highly customized.
I suggest reviewing the manual page and the double-dash
--h option because Linux is very
particular about the format for printing out and adjusting dates and
The default without options is the current time. The option
--date shows a time other than now,
and --set is for setting time.
And now you know how to do that.
So why is date an important command?
Well, most of us already know what time it is, but date helps us print
system time on reports. Also, accurately calendering jobs is dependent
on you ensuring that the system time is correct.
And now you know how to do that.
Okay, the best way to embed this in your memory is by typing in your
own terminal window.
Find this on your Mac using a program called Terminal. On Linux use
Terminal or Konsole, and currently Microsoft is adding this
functionality to Windows.
Here we go, type date to see date
and time, in standard format.
Mon Oct 10 12:49:43 PDT 2016
And to see the extensive list of formats, type double-dash
(first 25 lines trimmed)
FORMAT controls the output. Interpreted sequences are:
%% a literal %
%a locale's abbreviated weekday name (e.g., Sun)
%A locale's full weekday name (e.g., Sunday)
%b locale's abbreviated month name (e.g., Jan)
%B locale's full month name (e.g., January)
%c locale's date and time (e.g., Thu Mar 3 23:05:25 2005)
%C century; like %Y, except omit last two digits (e.g., 20)
%d day of month (e.g., 01)
%D date; same as %m/%d/%y
%e day of month, space padded; same as %_d
%F full date; same as %Y-%m-%d
%g last two digits of year of ISO week number (see %G)
%G year of ISO week number (see %V); normally useful only with %V
%h same as %b
%H hour (00..23)
%I hour (01..12)
%j day of year (001..366)
%k hour, space padded ( 0..23); same as %_H
%l hour, space padded ( 1..12); same as %_I
%m month (01..12)
%M minute (00..59)
%n a newline
%N nanoseconds (000000000..999999999)
%p locale's equivalent of either AM or PM; blank if not known
%P like %p, but lower case
%r locale's 12-hour clock time (e.g., 11:11:04 PM)
%R 24-hour hour and minute; same as %H:%M
%s seconds since 1970-01-01 00:00:00 UTC
%S second (00..60)
%t a tab
%T time; same as %H:%M:%S
%u day of week (1..7); 1 is Monday
%U week number of year, with Sunday as first day of week (00..53)
%V ISO week number, with Monday as first day of week (01..53)
%w day of week (0..6); 0 is Sunday
%W week number of year, with Monday as first day of week (00..53)
%x locale's date representation (e.g., 12/31/99)
%X locale's time representation (e.g., 23:13:48)
%y last two digits of year (00..99)
%z +hhmm numeric time zone (e.g., -0400)
%:z +hh:mm numeric time zone (e.g., -04:00)
%::z +hh:mm:ss numeric time zone (e.g., -04:00:00)
%:::z numeric time zone with : to necessary precision (e.g., -04, +05:30)
%Z alphabetic time zone abbreviation (e.g., EDT)
By default, date pads numeric fields with zeroes.
The following optional flags may follow '%':
- (hyphen) do not pad the field
_ (underscore) pad with spaces
0 (zero) pad with zeros
^ use upper case if possible
# use opposite case if possible
After any flags comes an optional field width, as a decimal number;
then an optional modifier, which is either
E to use the locale's alternate representations if available, or
O to use the locale's alternate numeric symbols if available.
Convert seconds since the epoch (1970-01-01 UTC) to a date
$ date --date='@2147483647'
Show the time on the west coast of the US (use tzselect(1) to find TZ)
$ TZ='America/Los_Angeles' date
Show the local time for 9AM next Friday on the west coast of the US
$ date --date='TZ="America/Los_Angeles" 09:00 next Fri'
(last 4 lines trimmed)
Then Shift-PgUp to scroll,
Shift-PgDn. Take a look at that.
It's quite a list. Wow!
Next, let's use double-dash
--date="yesterday" to show
$ date --date="yesterday"
Sun Oct 9 12:50:11 PDT 2016
And then last, let's see the date yesterday, using a plus and this
$ date --date="yesterday" +%D
A Final Tip
Okay now you know how to use date.
And you know the syntax for commands, options and arguments.
One last tip about the date command.
I suggest reviewing the user manual for
date and be careful when setting the
system time. Next we'll cover another time-related command.
Okay, thanks for visiting today. I hope this was a fun introduction
to the date command.
Learn More About The Series
For an overview of the 100 videos, the 8 quizzes, a cheat sheet, the
categories and a Q&A section, visit: