File: coreutils.info,  Node: Formatting file timestamps,  Next: Formatting the file names,  Prev: General output formatting,  Up: ls invocation

10.1.5 Formatting file timestamps
---------------------------------

By default, file timestamps are listed in abbreviated form, using a date
like ‘Mar 30  2020’ for non-recent timestamps, and a date-without-year
and time like ‘Mar 30 23:45’ for recent timestamps.  This format can
change depending on the current locale as detailed below.

   A timestamp is considered to be “recent” if it is less than six
months old, and is not dated in the future.  If a timestamp dated today
is not listed in recent form, the timestamp is in the future, which
means you probably have clock skew problems which may break programs
like ‘make’ that rely on file timestamps.  *Note File timestamps::.

   Timestamps are listed according to the time zone rules specified by
the ‘TZ’ environment variable, or by the system default rules if ‘TZ’ is
not set.  *Note Specifying the Time Zone with ‘TZ’: (libc)TZ Variable.

   The following option changes how file timestamps are printed.

‘--time-style=STYLE’
     List timestamps in style STYLE.  The STYLE should be one of the
     following:

     ‘+FORMAT’
          List timestamps using FORMAT, where FORMAT is interpreted like
          the format argument of ‘date’ (*note date invocation::).  For
          example, ‘--time-style="+%Y-%m-%d %H:%M:%S"’ causes ‘ls’ to
          list timestamps like ‘2020-03-30 23:45:56’.  As with ‘date’,
          FORMAT’s interpretation is affected by the ‘LC_TIME’ locale
          category.

          If FORMAT contains two format strings separated by a newline,
          the former is used for non-recent files and the latter for
          recent files; if you want output columns to line up, you may
          need to insert spaces in one of the two formats.

     ‘full-iso’
          List timestamps in full using ISO 8601-like date, time, and
          time zone components with nanosecond precision, e.g.,
          ‘2020-07-21 23:45:56.477817180 -0400’.  This style is
          equivalent to ‘+%Y-%m-%d %H:%M:%S.%N %z’.

          This is useful because the time output includes all the
          information that is available from the operating system.  For
          example, this can help explain ‘make’’s behavior, since GNU
          ‘make’ uses the full timestamp to determine whether a file is
          out of date.

     ‘long-iso’
          List ISO 8601 date and time components with minute precision,
          e.g., ‘2020-03-30 23:45’.  These timestamps are shorter than
          ‘full-iso’ timestamps, and are usually good enough for
          everyday work.  This style is equivalent to ‘+%Y-%m-%d %H:%M’.

     ‘iso’
          List ISO 8601 dates for non-recent timestamps (e.g.,
          ‘2020-03-30 ’), and ISO 8601-like month, day, hour, and minute
          for recent timestamps (e.g., ‘03-30 23:45’).  These timestamps
          are uglier than ‘long-iso’ timestamps, but they carry nearly
          the same information in a smaller space and their brevity
          helps ‘ls’ output fit within traditional 80-column output
          lines.  The following two ‘ls’ invocations are equivalent:

               newline='
               '
               ls -l --time-style="+%Y-%m-%d $newline%m-%d %H:%M"
               ls -l --time-style="iso"

     ‘locale’
          List timestamps in a locale-dependent form.  For example, a
          French locale might list non-recent timestamps like ‘30
          mars   2020’ and recent timestamps like ‘30 mars  23:45’.
          Locale-dependent timestamps typically consume more space than
          ‘iso’ timestamps and are harder for programs to parse because
          locale conventions vary so widely, but they are easier for
          many people to read.

          The ‘LC_TIME’ locale category specifies the timestamp format.
          The default POSIX locale uses timestamps like ‘Mar 30  2020’
          and ‘Mar 30 23:45’; in this locale, the following two ‘ls’
          invocations are equivalent:

               newline='
               '
               ls -l --time-style="+%b %e  %Y$newline%b %e %H:%M"
               ls -l --time-style="locale"

          Other locales behave differently.  For example, in a German
          locale, ‘--time-style="locale"’ might be equivalent to
          ‘--time-style="+%e. %b %Y $newline%e. %b %H:%M"’ and might
          generate timestamps like ‘30. Mär 2020 ’ and ‘30. Mär 23:45’.

     ‘posix-STYLE’
          List POSIX-locale timestamps if the ‘LC_TIME’ locale category
          is POSIX, STYLE timestamps otherwise.  For example, the
          ‘posix-long-iso’ style lists timestamps like ‘Mar 30  2020’
          and ‘Mar 30 23:45’ when in the POSIX locale, and like
          ‘2020-03-30 23:45’ otherwise.

   You can specify the default value of the ‘--time-style’ option with
the environment variable ‘TIME_STYLE’; if ‘TIME_STYLE’ is not set the
default style is ‘locale’.  GNU Emacs 21.3 and later use the ‘--dired’
option and therefore can parse any date format, but if you are using
Emacs 21.1 or 21.2 and specify a non-POSIX locale you may need to set
‘TIME_STYLE="posix-long-iso"’.

   To avoid certain denial-of-service attacks, timestamps that would be
longer than 1000 bytes may be treated as errors.