How to change the output of `date` back to 24-hour format

dateglibclocaleupgrade

Apparently a recent change (in Glibc 2.29?) causes the date command to start printing times in 12-hour format:

$ date
Fri 23 Aug 2019 07:34:13 PM PDT

This is for my default locale

$ cat /etc/locale.conf 
LANG=en_US.UTF-8

How can I configure my system to go back to displaying dates in 24-hour format?

Best Answer

As suggested by jamespharvey20 on IRC, I just changed LC_TIME to another locale. I set it in /etc/locale.conf:

$ cat /etc/locale.conf
LANG=en_US.UTF-8
LC_TIME=en_GB

I also exported this value of LC_TIME in my shell profile, to avoid having to restart (I couldn't figure out how to get Systemd to reread the locale.conf). This seems a bit hacky but I think it's the best we came up with. Also, it preserves the new "DD MMM" format which I prefer to the old "MMM DD".

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Linux – Best practice to customize date/time format system-wide

As pointed out in some of the comments, you can either copy the rest of the sections and customize LC_TIME in your custom locales file, or configure LC_TIME in /etc/locale.conf. As the locale.conf(5) man-page suggests, you could also use the kernel commandline option locale.LC_TIME= to override the setting at boot time.

Shell – ps output with iso date format

Is there a way to output lstart in ISO format like YYYY-MM-DD HH:MM:SS?

With awk + date cooperation:

ps -eo lstart,pid,cmd --sort=start_time | awk '{ 
       cmd="date -d\""$1 FS $2 FS $3 FS $4 FS $5"\" +\047%Y-%m-%d %H:%M:%S\047"; 
       cmd | getline d; close(cmd); $1=$2=$3=$4=$5=""; printf "%s\n",d$0 }'

Alternative approach using ps etimes keyword(elapsed time since the process was started, in seconds):

ps -eo etimes,pid,cmd --sort=etimes | awk '{ 
       cmd="date -d -"$1"seconds +\047%Y-%m-%d %H:%M:%S\047"; 
       cmd | getline d; close(cmd); $1=""; printf "%s\n",d$0 }'

date -d -"$1"seconds - difference between the current timestamp and elapsed time, will give the timestamp value of the process

Best Answer

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Linux – Best practice to customize date/time format system-wide

Shell – ps output with iso date format

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