File: coreutils.info,  Node: Padding and other flags,  Next: Setting the time,  Prev: Literal conversion specifiers,  Up: date invocation

21.1.4 Padding and other flags
------------------------------

Unless otherwise specified, ‘date’ normally pads numeric fields with
zeros, so that, for example, numeric months are always output as two
digits.  Most numeric fields are padded on the left.  However,
nanoseconds are padded on the right since they are commonly used after
decimal points in formats like ‘%s.%-N’.  Also, seconds since the Epoch
are not padded since there is no natural width for them.

   The following optional flags can appear after the ‘%’:

‘-’
     (hyphen) Do not pad the field; useful if the output is intended for
     human consumption.  This is a GNU extension.  As a special case,
     ‘%-N’ outputs only enough trailing digits to not lose information,
     assuming that the timestamp’s resolution is the same as the current
     hardware clock.  For example, if the hardware clock resolution is 1
     microsecond, ‘%s.%-N’ outputs something like ‘1640890100.395710’.

‘_’
     (underscore) Pad with spaces; useful if you need a fixed number of
     characters in the output, but zeros are too distracting.  This is a
     GNU extension.
‘0’
     (zero) Pad with zeros even if the conversion specifier would
     normally pad with spaces.
‘+’
     Pad with zeros, like ‘0’.  In addition, precede any year number
     with ‘+’ if it exceeds 9999 or if its field width exceeds 4;
     similarly, precede any century number with ‘+’ if it exceeds 99 or
     if its field width exceeds 2.  This supports ISO 8601 formats for
     dates far in the future; for example, the command ‘date
     --date=12019-02-25 +%+13F’ outputs the string ‘+012019-02-25’.
‘^’
     Use upper case characters if possible.  This is a GNU extension.
‘#’
     Use opposite case characters if possible.  A field that is normally
     upper case becomes lower case, and vice versa.  This is a GNU
     extension.

Here are some examples of padding:

     date +%d/%m -d "Feb 1"
     ⇒ 01/02
     date +%-d/%-m -d "Feb 1"
     ⇒ 1/2
     date +%_d/%_m -d "Feb 1"
     ⇒  1/ 2

   You can optionally specify the field width (after any flag, if
present) as a decimal number.  If the natural size of the output of the
field has less than the specified number of characters, the result is
normally written right adjusted and padded to the given size.  For
example, ‘%9B’ prints the right adjusted month name in a field of width
9.  Nanoseconds are left adjusted, and are truncated or padded to the
field width.

   An optional modifier can follow the optional flag and width
specification.  The modifiers are:

‘E’
     Use the locale’s alternate representation for date and time.  This
     modifier applies to the ‘%c’, ‘%C’, ‘%x’, ‘%X’, ‘%y’ and ‘%Y’
     conversion specifiers.  In a Japanese locale, for example, ‘%Ex’
     might yield a date format based on the Japanese Emperors’ reigns.

‘O’
     Use the locale’s alternate numeric symbols for numbers.  This
     modifier applies only to numeric conversion specifiers.

   If the format supports the modifier but no alternate representation
is available, it is ignored.

   POSIX specifies the behavior of flags and field widths only for ‘%C’,
‘%F’, ‘%G’, and ‘%Y’ (all without modifiers), and requires a flag to be
present if and only if a field width is also present.  Other
combinations of flags, field widths and modifiers are GNU extensions.