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I am following the answer in https://askubuntu.com/a/162714/146591 to generate a custom locale on my system. Many of the fields that can be configured in a locale are input for the date utility (https://www.man7.org/linux/man-pages/man1/date.1.html).

I would like to change some of the output of time format. Concretely, I want to show the clock in base-12 notation, such that when 09:08 (base 10) is equivalent to 09:08 (base 12), 12:10 is equivalent to 10:A0 (base 12, if we use A and B for the values after 9).

I would like to configure my locale section LC_TIME as

LC_TIME
copy "nl_NL"

t_fmt "$(((date +%H) % 12))$(((date +%M) % 12))"

END LC_TIME

but then more complicated to achieve what I need. I can make a script available system wide that would output the correct format, but this script would still need to be called by the locale library. It should not be passed as input parameters to the date utility.

Is any of this possible?

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1 Answer 1

Reset to default
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The value of that locale setting is intended to be passed (by the application after it has queried it using something like nl_langinfo(T_FMT) in C) to the strftime() function, so you're limited to what that function supports.

It doesn't support specifying a different base for outputting numbers, let alone interpreting shell code, but it supports a %OH and %OM that are like %H and %M except that they use the alt_digits to represent numbers from decimal 0 to decimal 99, so you could use:

d_t_fmt "%a %d %b %Y %OH:%OM %Z"
t_fmt "%OH:%OM"
date_fmt "%a %e %b %Y %OH:%OM %Z"
alt_digits  "00";"01";"02";"03";"04";"05";"06";"07";"08";"09";"0A";"0B";/
            "10";"11";"12";"13";"14";"15";"16";"17";"18";"19";"1A";"1B";/
            "20";"21";"22";"23";"24";"25";"26";"27";"28";"29";"2A";"2B";/
            "30";"31";"32";"33";"34";"35";"36";"37";"38";"39";"3A";"3B";/
            "40";"41";"42";"43";"44";"45";"46";"47";"48";"49";"4A";"4B";/
            "50";"51";"52";"53";"54";"55";"56";"57";"58";"59";"5A";"5B";/
            "60";"61";"62";"63";"64";"65";"66";"67";"68";"69";"6A";"6B";/
            "70";"71";"72";"73";"74";"75";"76";"77";"78";"79";"7A";"7B";/
            "80";"81";"82";"83"

And copy the rest from nl_NL and then (here with the locale compiled into ~/.locales/base12time):

$ LOCPATH=~/.locales LC_ALL=base12time date -d 2020-06-19T12:10:08
vr 19 jun 2020 10:0A BST
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  • Thank you, this is great! I did not find the alt_digits locale specification. Commented Oct 19, 2024 at 14:45

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