Let's say you have a file date.sh. The following is the absoulte minimal code needed to produce the date in a BASH script.

#!/bin/bash
date

Running this script will produce the following:

Wed Nov 30 19:01:23 CST 2016

Echo date inline

Let's say we want to add some text before the date.

#!/bin/bash
echo "The current date and time is $(date)"

Running this script will produce the following:

The current date and time is Wed Nov 30 19:01:23 CST 2016

Format the date

Typically, the entire date string, with the date of the week, month, date, time, time zone, and year, is not what we want. We can customize this output by selecting the particular elements we want to display.

#!/bin/bash
echo "The current date is $(date '+%m-%d-%Y')"

Running this script will produce the following:

The current date and time is 11-30-2016

%F can be used for the year (and %T for the time) to reduce the amount of options needed to format the date.

#!/bin/bash
echo "The current date is $(date +%F)"

Following are commonly used options.

UTC timezone

The date command will return the date for the timezone of your Linux system. The -u or --utc or --universal flag can be used to return the date in the UTC timezone.

date --utc

Or like this.

utc_time=$(TZ=GMT date)
echo $utc_time

Or like this.

export TZ=GMT
utc_time=$(date)
echo $utc_time

Variable

We can put the date in a variable and then use an if / else statement to display certain text based on the statement.

#!/bin/bash
today=$(date +%m-%d-%Y)

if [ $today == "2016-11-30" ]
then
  echo "True"
else
  echo "False"
fi

Running this script will produce the following:

False

Future / Past date

The -d or --date option can be used to modify the date, such as going forward 14 days.

#!/bin/bash
two_weeks=$(date '+%m-%d-%Y' --date '+14 days')

Or 1 year ago.

#!/bin/bash
one_year_ago=$(date '+%m-%d-%Y' --date '-1 year')