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MODIFIED: parse_time/2,3: interpret missing timezone as local time.
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This patch fixes parsing ``YYYY-MM``, which used to be a day too early.
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@JanWielemaker
JanWielemaker committed Sep 30, 2024
1 parent f0b87bf commit 91ad94b
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148 changes: 82 additions & 66 deletions library/date.pl
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Author: Jan Wielemaker and Willem Robert van Hage
E-mail: wielemak@science.uva.nl
WWW: http://www.swi-prolog.org
Copyright (c) 2006-2014, University of Amsterdam
Copyright (c) 2006-2024, University of Amsterdam
SWI-Prolog Solutions b.v.
All rights reserved.
Redistribution and use in source and binary forms, with or without
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%
% Fri, 08 Dec 2006 15:29:44 GMT
%
% All components except for the time zone are obligatory.
% If the time zone is omitted, the time is interpreted as
% _local time_.
%
% * iso_8601
% Commonly used in XML documents. Actually the XML RFC3339
% is a _profile_ of ISO8601. For example
%
% 2006-12-08T15:29:44Z
%
% The ISO8601 format allows removing components from the
% right, returning the lowest time stamp in the specified
% internal. If a time is specified but no time zone, the
% time stamp is computed for the _local time_. If only
% the date components are specified, the stamp uses UTC.
% To compute the start of a day in local time, use
% e.g. ``2006-12-08T00``.
%
% @arg Text is an atom, string or list of character _codes_.
% @see xsd_time_string/3 from library(sgml) implements RFC3339
% strictly.

parse_time(Text, Stamp) :-
parse_time(Text, _Format, Stamp).

parse_time(Text, Format, Stamp) :-
atom_codes(Text, Codes),
to_codes(Text, Codes),
phrase(date(Format, Y,Mon,D,H,Min,S,UTCOffset), Codes),
!,
date_time_stamp(date(Y,Mon,D,H,Min,S,UTCOffset,-,-), Stamp).

date(iso_8601, Yr, Mon, D, H, Min, S, 0) --> % BC
"-", date(iso_8601, Y, Mon, D, H, Min, S, 0),
tz_dst(time(H,Min,S), UTCOffset, TZ, DST),
date_time_stamp(date(Y,Mon,D,H,Min,S,UTCOffset,TZ,DST), Stamp).

to_codes(In, Codes) :-
( is_list(In)
-> Codes = In
; atom_codes(In, Codes)
).

tz_dst(_Time, UTCOffset, TZ, DST), nonvar(UTCOffset) =>
TZ = (-), DST = (-).
tz_dst(time(H,M,S), UTCOffset, TZ, DST), var(H), var(M), var(S) =>
UTCOffset = 0, TZ = (-), DST = (-).
tz_dst(_, _, _, _) =>
true.

date(iso_8601, Yr, Mon, D, H, Min, S, UTCOffset) --> % BC
"-", date(iso_8601, Y, Mon, D, H, Min, S, UTCOffset),
{ Yr is -1 * Y }.
date(iso_8601, Y, Mon, D, H, Min, S, 0) -->
date(iso_8601, Y, Mon, D, H, Min, S, UTCOffset) -->
year(Y),
iso_8601_rest(Y, Mon, D, H, Min, S).
date(rfc_1123, Y, Mon, D, Hr, Min, Sec, 0) --> % RFC 1123: "Fri, 08 Dec 2006 15:29:44 GMT"
day_name(_), ", ", ws,
iso_8601_rest(Y, Mon, D, H, Min, S, UTCOffset).
date(rfc_1123, Y, Mon, D, H, M, S, UTCOffset) -->
day_name(_), ", ", ws, % RFC 1123: "Fri, 08 Dec 2006 15:29:44 GMT"
day_of_the_month(D), ws,
month_name(Mon), ws,
year(Y), ws,
hour(H), ":", minute(M), ":", second(S), ws,
timezone(DH, DM, DS),
{ Hr is H + DH, Min is M + DM, Sec is S + DS }.

timezone(UTCOffset).

%! iso_8601_rest(+Year:int, -Mon, -Day, -H, -M, -S)
%! iso_8601_rest(+Year:int, -Mon, -Day, -H, -M, -S, -UTCOffset)
%
% Process ISO 8601 time-values after parsing the 4-digit year.

iso_8601_rest(_, Mon, D, H, Min, S) -->
iso_8601_rest(_, Mon, D, H, Min, S, UTCOffset) -->
"-", month(Mon), "-", day(D),
opt_time(H, Min, S).
iso_8601_rest(_, Mon, 0, 0, 0, 0) -->
opt_time(H, Min, S, UTCOffset).
iso_8601_rest(_, Mon, _, _, _, _, _) -->
"-", month(Mon).
iso_8601_rest(_, Mon, D, H, Min, S) -->
iso_8601_rest(_, Mon, D, H, Min, S, UTCOffset) -->
month(Mon), day(D),
opt_time(H, Min, S).
iso_8601_rest(_, 1, D, H, Min, S) -->
opt_time(H, Min, S, UTCOffset).
iso_8601_rest(_, 1, D, H, Min, S, UTCOffset) -->
"-", ordinal(D),
opt_time(H, Min, S).
iso_8601_rest(Yr, 1, D, H, Min, S) -->
opt_time(H, Min, S, UTCOffset).
iso_8601_rest(Yr, 1, D, H, Min, S, UTCOffset) -->
"-W", week(W), "-", day_of_the_week(DW),
opt_time(H, Min, S),
opt_time(H, Min, S, UTCOffset),
{ week_ordinal(Yr, W, DW, D) }.
iso_8601_rest(Yr, 1, D, H, Min, S) -->
iso_8601_rest(Yr, 1, D, H, Min, S, UTCOffset) -->
"W", week(W), day_of_the_week(DW),
opt_time(H, Min, S),
opt_time(H, Min, S, UTCOffset),
{ week_ordinal(Yr, W, DW, D) }.
iso_8601_rest(Yr, 1, D, 0, 0, 0) -->
iso_8601_rest(Yr, 1, D, _, _, _, _) -->
"W", week(W),
{ week_ordinal(Yr, W, 1, D) }.

opt_time(Hr, Min, Sec) -->
("T";" "), !, iso_time(Hr, Min, Sec).
opt_time(0, 0, 0) --> "".
opt_time(Hr, Min, Sec, UTCOffset) -->
("T";" "), !, iso_time(Hr, Min, Sec), timezone(UTCOffset).
opt_time(_H, _M, _S, _UTCOffset) --> "".


% TIMEX2 ISO: "2006-12-08T15:29:44 UTC" or "20061208T"
iso_time(Hr, Min, Sec) -->
hour(H), ":", minute(M), ":", second(S),
timezone(DH, DM, DS),
{ Hr is H + DH, Min is M + DM, Sec is S + DS }.
iso_time(Hr, Min, Sec) -->
hour(H), ":", minute(M),
timezone(DH, DM, DS),
{ Hr is H + DH, Min is M + DM, Sec is DS }.
iso_time(Hr, Min, Sec) -->
hour(H), minute(M), second(S),
timezone(DH, DM, DS),
{ Hr is H + DH, Min is M + DM, Sec is S + DS }.
iso_time(Hr, Min, Sec) -->
hour(H), minute(M),
timezone(DH, DM, DS),
{ Hr is H + DH, Min is M + DM, Sec is DS }.
iso_time(Hr, Min, Sec) -->
hour(H),
timezone(DH, DM, DS),
{ Hr is H + DH, Min is DM, Sec is DS }.
iso_time(H, M, S) -->
hour(H), ":", minute(M), ":", second(S).
iso_time(H, M, _) -->
hour(H), ":", minute(M).
iso_time(H, M, S) -->
hour(H), minute(M), second(S).
iso_time(H, M, _) -->
hour(H), minute(M).
iso_time(H, _, _) -->
hour(H).

% FIXME: deal with leap seconds
timezone(Hr, Min, 0) -->
"+", hour(H), ":", minute(M), { Hr is -1 * H, Min is -1 * M }.
timezone(Hr, Min, 0) -->
"+", hour(H), minute(M), { Hr is -1 * H, Min is -1 * M }.
timezone(Hr, 0, 0) -->
"+", hour(H), { Hr is -1 * H }.
timezone(Hr, Min, 0) -->
"-", hour(H), ":", minute(M), { Hr is H, Min is M }.
timezone(Hr, Min, 0) -->
"-", hour(H), minute(M), { Hr is H, Min is M }.
timezone(Hr, 0, 0) -->
"-", hour(H), { Hr is H }.
timezone(0, 0, 0) -->
timezone(UTCOffset) -->
"+", hour(H), ":", minute(M), { UTCOffset is -(H*3600+M*60) }.
timezone(UTCOffset) -->
"+", hour(H), minute(M), { UTCOffset is -(H*3600+M*60) }.
timezone(UTCOffset) -->
"+", hour(H), { UTCOffset is -(H*3600) }.
timezone(UTCOffset) -->
"-", hour(H), ":", minute(M), { UTCOffset is H*3600+M*60 }.
timezone(UTCOffset) -->
"-", hour(H), minute(M), { UTCOffset is H*3600+M*60 }.
timezone(UTCOffset) -->
"-", hour(H), { UTCOffset is H*3600 }.
timezone(0) -->
"Z".
timezone(0, 0, 0) -->
timezone(0) -->
ws, "UTC".
timezone(0, 0, 0) -->
ws, "GMT". % remove this?
timezone(0, 0, 0) -->
timezone(0) -->
ws, "GMT".
timezone(_) --> % unknown
[].

day_name(0) --> "Sun".
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2 changes: 1 addition & 1 deletion src/Tests/library/test_date.pl
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parse_time('2006-12-08', iso_8601, T).
test(iso_8601, T =:= 1165536000) :-
parse_time('20061208', iso_8601, T).
test(iso_8601, T =:= 1164844800) :-
test(iso_8601, T =:= 1164931200) :-
parse_time('2006-12', iso_8601, T).
test(iso_8601, T =:= 1165536000) :-
parse_time('2006-W49-5', iso_8601, T).
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