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time_and_date

At the Command Line

Time and Date

Handy Timezone Conversion Web Page

Calendar

Display a Calendar

cal -3

Display a Calendar for a Particular Month and Year

cal 9 1752

Today's Date in a Full-year Calendar

cal -y | tr '\n' '|' | sed "s/^/ /;s/$/ /;s/ $(date +%e) / $(date +%e | sed 's/./#/g') /$(date +%m | sed s/^0//)" | tr '|' '\n'

What Date is it this Friday

date -d fri

What Day does Christmas Fall On

date --date='25 Dec' +%A

Date/Time Conversion

Convert Seconds Since the Epoch (1970-01-01 UTC) to Date

date --date='@2147483647'

Use the Date Command to do Timezone Conversion

date -d 'tomorrow 19:00 UTC-08'

Email a Reminder

 echo "mail -s 'get the train' P@draigBrady.com > /dev/null" | at 17:45

Time a Command

time command

Start a timer

time cat

Enter control-D to stop.

Date/Time and Scripts

Run a Script at a Certain Time

note: /usr/share/doc/at/timespec has the specs for time specification. The time is entered in GNU date format.

sudo at -f /home/andrew/bin/myscript.sh 16:00 Friday

To help deal with timezone conversion: http://www.timeanddate.com/worldclock/converter.html

Exit a Script Unless it's the Last Day of the Month

[ $(date -d "tomorrow" +%d) = "01" ] || exit

UTC

Coordinated Universal Time

World-connected servers commonly run on UTC, so it is necessary to deal with the difference between wherever you are and UTC.

Get Current UTC Time

TZ=':UTC' && date

Get Current Time in Los Angeles

TZ=America/Los_Angeles && date

Calculate Time from a Specified Timezone

TZ=':America/Los_Angeles' && date -d "+7 hours"

another example:

TZ=':America/Los_Angeles' && date -d "+ 2weeks +7 hours"

Timezones

Show the Server's Timezone

cat /etc/timezone
perl -E 'use POSIX; print strftime("%Z", localtime()), "\n";'

View Available Timezones

tzselect is a menu driven program that will allow you to find a timezone. It will not allow the server's timezone to be changed, but will show you the TZ value that you can use to do so with “sudo dpkg-reconfigure tzdata”.

tzselect

tzselect man page: http://manpages.ubuntu.com/manpages/precise/man1/tzselect.1.html

Change the Server's Timezone

sudo dpkg-reconfigure tzdata

time_and_date.txt · Last modified: 2015/05/31 21:20 (external edit)