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Check epoch date

Checking epoch dates with bash

Assuming you are given a date in millis of 1677628800000, you can use bash for some time calculations...

Note: This can be useful if you are checking the start date or expiration date of an Elasticsearch license, as it is provided in millis.

using bash for integer division

To perform integer division, you can use the shell: 

$ echo $(( var1 / var2 ))
0

The $(( ... )) syntax is known as an arithmetic expansion.

convert millis to epoch

First, convert the millis to epoch time by dividing it by 1000: 

$ echo $((1677628800000/1000))
1677628800

This returns 1677628800, which is what we will use for our calculations. You can also use @$((1677628800000/1000)) instead, if you would prefer.

formatting the date

Printing a date without any formatting: 

$ date -d @1677628800
Wed Mar  1 00:00:00 UTC 2023

Format the date as mm-dd-yy: 

$ date -d @1677628800 +"%m-%d-%y"
03-01-23

Format the date as mm/dd/yy: 

$ date -d @1677628800 +"%D"
03/01/23

Format the date as mm-dd-yyyy: 

$ date -d @1677628800 +"%m-%d-%Y"
03-01-2023

Format the date as Month dd yyyy: 

$ date -d @1677628800 +"%B %d %Y"
March 01 2023

Format the date as Month dd, yyyy: 

$ date -d @1677628800 +"%B %d, %Y"
March 01, 2023

Format the date as yyyymmdd: 

$ date -d @1677628800 +"%Y%m%d"
20230301

days since a past date

The following command will print how long it has been since 1677628800, which is Wednesday March 1, 2023: 

$ echo $(expr '(' $(date +%s) + 86399 - $(date -d @1677628800 +%s) ')' / 86400) "days since $(date -d @1677628800 +"%B %d, %Y")"
484 days since March 01, 2023

Same as above, but using @$((1677628800000/1000)) instead: 

$ echo $(expr '(' $(date +%s) + 86399 - $(date -d @$((1677628800000/1000)) +%s) ')' / 86400) "days since $(date -d @$((1677628800000/1000)) +"%B %d, %Y")"
484 days since March 01, 2023

days until a date

The following command will print days until deadline against 1677628800; it will return a negative number since this is in the past: 

$ echo $(expr '(' $(date -d @1677628800 +%s) - $(date +%s) + 86399 ')' / 86400) "days until deadline"
-482 days until deadline

Same as above, but using @$((1677628800000/1000)) instead: 

$ echo $(expr '(' $(date -d @$((1677628800000/1000)) +%s) - $(date +%s) + 86399 ')' / 86400) "days until deadline"
-482 days until deadline

more fancy

The following command will print both the days until deadline and the deadline date against 1677628800; it will return a negative number since this is in the past: 

$ echo $(expr '(' $(date -d @1677628800 +%s) - $(date +%s) + 86399 ')' / 86400) "days until the $(date -d @1677628800 +"%B %d, %Y") deadline"
-482 days until the March 01, 2023 deadline

Same as above, but using @$((1677628800000/1000)) instead: 

$ echo $(expr '(' $(date -d @$((1677628800000/1000)) +%s) - $(date +%s) + 86399 ')' / 86400) "days until the $(date -d @$((1677628800000/1000)) +"%B %d, %Y") deadline"
-482 days until the March 01, 2023 deadline

  • https://unix.stackexchange.com/questions/453703/determine-if-date-is-beyond-90-days-in-bash
  • https://dev.to/dm8ry/bash-script-to-find-the-difference-between-an-epoch-timestamp-and-the-current-date-1hik
  • https://stackoverflow.com/questions/16311688/bash-convert-epoch-to-date-showing-wrong-time
  • https://stackoverflow.com/questions/6282059/how-do-you-print-the-days-until-a-deadline-from-the-command-line
  • https://www.networkworld.com/article/968163/counting-down-the-days-using-bash.html
  • https://www.cyberciti.biz/faq/linux-unix-formatting-dates-for-display/
  • https://stackoverflow.com/questions/4946785/how-to-find-the-difference-in-days-between-two-dates
  • https://stackoverflow.com/questions/1706882/get-the-date-a-day-before-current-time-in-bash
  • https://stackoverflow.com/questions/67613190/how-to-find-30-days-older-epoch-time-in-ms-from-current-time-in-shell-script
  • https://stackoverflow.com/questions/66920940/parsing-the-date-to-calculate-days-until-cert-expiry-from-a-shell-script
  • https://www.epochconverter.com/
  • https://serverfault.com/questions/1044369/how-do-i-get-the-current-time-in-milliseconds-in-a-shell-script-in-buildroot-env
  • https://stackoverflow.com/questions/16548528/linux-command-to-get-time-in-milliseconds
  • https://serverfault.com/questions/151109/how-do-i-get-the-current-unix-time-in-milliseconds-in-bash
  • https://stackoverflow.com/questions/62025091/how-to-convert-column-with-millisecond-timestamp-to-date-in-a-file-using-bash
  • https://stackoverflow.com/questions/16311688/bash-convert-epoch-to-date-showing-wrong-time
  • https://stackoverflow.com/questions/50466939/get-end-of-day-epoch-in-shell-script-bash
  • https://stackoverflow.com/questions/70781768/remove-millisecond-from-echo-time-bash
  • https://unix.stackexchange.com/questions/2987/how-do-i-convert-an-epoch-timestamp-to-a-human-readable-format-on-the-cli