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Given a date and time in a format that is not recognized by date, how can I get date to recognize the date and time?

For example:

$ date -d "09SEP2012:23:58:46"
date: invalid date `09SEP2012:23:58:46'
$ date -d "09SEP2012:23:58:46" --magic-option "ddMMMYYY:hh:mm:ss"
Sun Sep  9 23:58:46 MDT 2012

Does --magic-option exist? If not, is there a more elegant way to solve this rather than using sed to transform the input into a well-formed date string?

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3 Answers 3

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Neither POSIX nor GNU date have --magic-option. FreeBSD calls it -f (with a syntax similar to date's output format specifiers, not the one you propose).

Your date is very close to being recognized by GNU date: all it takes is replacing the colon that separates the date from the time by a space.

date -d "$(echo "09SEP2012:23:58:46" | sed 's/:/ /')"
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  • 1
    and with custom formats? Only way to go are regular expressions? this is horrible :-(
    – phil294
    Dec 22, 2017 at 19:39
  • 2
    You can't parse dates without knowing something about the format they're in, the classical example being 01/02/03. Dec 22, 2017 at 19:50
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I wrote a bunch of tools (dateutils) that deal with dates and times in a more script-friendly way. Your magic option there is --input-format|-i, e.g.:

dconv -i '%d%b%Y:%H:%M:%S' "09SEP2012:23:58:46"
=>
  2012-09-09T23:58:46

While dconv does not directly support date's output format (it doesn't confer TZ or anything in the environment), there's a tool strptime in dateutils that does support the %Z format specifier.

1

If you're using an environment like Ubuntu that has busybox installed, you can do:

busybox date -D "$input_format" -d "$input" +"$output_format"

such as

$ busybox date -D "%m/%d/%Y" -d "01/14/2022" +"%Y-%m-%d"
2022-01-14

Note that using + to format the output string is not documented in the busybox man page. Also, this might not work with %Z timezone format.

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