Availability:built-in
format_time(+Out,
+Format, +StampOrDateTime)Modelled after POSIX strftime(), using GNU extensions. Out
is a destination as specified with with_output_to/2. Format
is an atom or string with the following conversions. Conversions start
with a percent (%) character.152Descriptions
taken from Linux Programmer's Manual
StampOrDateTime is either a numeric time-stamp, a term
date(Y,M,D,H,M,S,O,TZ,DST)
or a term date(Y,M,D)
.
a
The abbreviated weekday name according to the current locale. Use
format_time/4
for POSIX locale.
A
The full weekday name according to the current locale. Use
format_time/4
for POSIX locale.
b
The abbreviated month name according to the current locale. Use
format_time/4
for POSIX locale.
B
The full month name according to the current locale. Use
format_time/4
for POSIX locale.
c
The preferred date and time representation for the current locale.
C
The century number (year/100) as a 2-digit integer.
d
The day of the month as a decimal number (range 01 to 31).
D
Equivalent to %m/%d/%y. (For Americans only. Americans should note that
in other countries %d/%m/%y is rather common. This means that in an
international context this format is ambiguous and should not be used.)
e
Like %d, the day of the month as a decimal number, but a leading zero is
replaced by a space.
E
Modifier. Not implemented.
f
Number of microseconds. The f
can be prefixed by an integer
to print the desired number of digits. E.g., %3f
prints
milliseconds. This format is not covered by any standard, but available
with different format specifiers in various incarnations of the strftime()
function.
F
Equivalent to %Y-%m-%d (the ISO 8601 date format).
g
Like %G, but without century, i.e., with a 2-digit year (00-99).
G
The ISO 8601 year with century as a decimal number. The 4-digit year
corresponding to the ISO week number (see %V). This has the same format
and value as %y, except that if the ISO week number belongs to the
previous or next year, that year is used instead.
V
The ISO 8601:1988 week number of the current year as a decimal number,
range 01 to 53, where week 1 is the first week that has at least 4 days
in the current year, and with Monday as the first day of the week. See
also %U and %W.
h
Equivalent to %b.
H
The hour as a decimal number using a 24-hour clock (range 00 to 23).
I
The hour as a decimal number using a 12-hour clock (range 01 to 12).
j
The day of the year as a decimal number (range 001 to 366).
k
The hour (24-hour clock) as a decimal number (range 0 to 23); single
digits are preceded by a blank. (See also %H.)
l
The hour (12-hour clock) as a decimal number (range 1 to 12); single
digits are preceded by a blank. (See also %I.)
m
The month as a decimal number (range 01 to 12).
M
The minute as a decimal number (range 00 to 59).
n
A newline character.
O
Modifier to select locale-specific output. Not implemented.
p
Either‘AM’or‘PM’according to the given time
value, or the corresponding strings for the current locale. Noon is
treated as‘pm’and midnight as‘am’.153Despite
the above claim, some locales yield am
or pm
in lower case.
P
Like %p but in lowercase:‘am’or‘pm’or a
corresponding string for the current locale.
r
The time in a.m. or p.m. notation. In the POSIX locale this is
equivalent to‘%I:%M:%S %p’.
R
The time in 24-hour notation (%H:%M). For a version including the
seconds, see %T below.
s
The number of seconds since the Epoch, i.e., since 1970-01-01 00:00:00
UTC.
S
The second as a decimal number (range 00 to 60). (The range is up to 60
to allow for occasional leap seconds.)
t
A tab character.
T
The time in 24-hour notation (%H:%M:%S).
u
The day of the week as a decimal, range 1 to 7, Monday being 1. See also %w.
U
The week number of the current year as a decimal number, range 00 to 53,
starting with the first Sunday as the first day of week 01. See also %V
and %W.
w
The day of the week as a decimal, range 0 to 6, Sunday being 0. See also %u.
W
The week number of the current year as a decimal number, range 00 to 53,
starting with the first Monday as the first day of week 01.
x
The preferred date representation for the current locale without the
time.
X
The preferred time representation for the current locale without the
date.
y
The year as a decimal number without a century (range 00 to 99).
Y
The year as a decimal number including the century.
z
The timezone as hour offset from GMT using the format HHmm. Required to
emit RFC822-conforming dates (using
’%a, %d %b %Y %T %z’
).
Our implementation supports
%:z
, which modifies the output to HH:mm as required by
XML-Schema. Note that both notations are valid in ISO 8601. The sequence %:z
is compatible to the GNU date(1) command.
Z
The timezone or name or abbreviation.
+
The date and time in date(1) format.
%
A literal‘%’character.
The table below gives some format strings for popular time
representations. RFC1123 is used by HTTP. The full implementation of
http_timestamp/2
as available from library(http/http_header)
is here.
http_timestamp(Time, Atom) :-
stamp_date_time(Time, Date, 'UTC'),
format_time(atom(Atom),
'%a, %d %b %Y %T GMT',
Date, posix).
Standard | Format string |
xsd | ’%FT%T%:z’ |
ISO8601 | ’%FT%T%z’ |
RFC822 | ’%a, %d %b %Y %T %z’ |
RFC1123 | ’%a, %d %b %Y %T GMT’ |