add Step by step guide for the date in Bash post

content/blog/2024-02-10-step-by-step-guide-for-the-date-in-bash.md

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+---
+author: Thomas Taylor
+categories:
+- programming
+date: '2024-02-10T22:00:07-05:00'
+description: How to get or print the date in a Bash script using the date command.
+tags:
+- bash
+title: 'Step by step guide for the date in Bash'
+---
+
+Unix provides a utility named `date`. As its name implies, it allows you to fetch your system's date.
+
+## Display the current date
+
+Displaying the current date is simple:
+
+```bash
+echo $(date)
+```
+
+Output:
+
+```text
+Sat Feb 10 21:29:37 EST 2024
+```
+
+The system date was printed with the timezone information.
+
+## Display the current date in UTC
+
+Similarly, we can display the current date in UTC (Coordinated Universal Time) using the `-u` flag:
+
+```bash
+echo $(date -u)
+```
+
+Output:
+
+```text
+Sun Feb 11 02:31:06 UTC 2024
+```
+
+The datetime was printed with the UTC timezone information.
+
+## Format the current date
+
+The default `date` output can easily be formatted in a bash script:
+
+```bash
+now="$(date '+%Y-%m-%d')"
+echo $now
+```
+
+Output:
+
+```text
+2024-02-10
+```
+
+The `date` manual page [showcases all the formatting options][1] available.
+
+## Getting a date from days ago
+
+Using the `-d` or `--date` option, we can display a different date:
+
+```bash
+now="$(date -d '2 days ago' '+%Y-%m-%d')"
+echo $now
+```
+
+Output:
+
+```text
+2024-02-08
+```
+
+For MacOS users, use the `-v` option:
+
+```bash
+now="$(date -v-2d '+%Y-%m-%d')"
+echo $now
+```
+
+## ISO-8601 date in Bash
+
+In 2011, the `-I` or `--iso-8601` [option was reintroduced][2] to the `date` utility.
+
+```bash
+now="$(date -Iseconds)"
+echo $now
+```
+
+Output:
+
+```text
+2024-02-11T02:47:41+00:00
+```
+
+For MacOS users, the `-I` option does not exist. You must format instead:
+
+```bash
+now="$(date -u '+%Y-%m-%dT%H:%M:%SZ')"
+echo $now
+```
+
+Output:
+
+```text
+2024-02-11T02:54:53Z
+```
+
+## Comparing two dates in Bash
+
+Using `-d` to convert the dates to unix timestamp, we can compare them.
+
+```bash
+dateOne=$(date -d 2022-02-10 +%s)
+dateTwo=$(date -d 2021-12-12 +%s)
+
+if [ $dateOne -ge $dateTwo ]; then
+    echo "woah!"
+fi
+```
+
+For MacOS users, the equivalent option is:
+
+```bash
+dateOne=$(date -j -f "%F" 2022-02-10 +"%s")
+dateTwo=$(date -j -f "%F" 2021-12-12 +"%s")
+
+if [ $dateOne -ge $dateTwo ]; then
+    echo "woah!"
+fi
+```
+
+[1]: https://man7.org/linux/man-pages/man1/date.1.html
+[2]: https://git.savannah.gnu.org/gitweb/?p=coreutils.git;a=commitdiff;h=2f1384b7