1#ifndef DATE_TIME_DST_RULES_HPP__
2#define DATE_TIME_DST_RULES_HPP__
3
4/* Copyright (c) 2002,2003, 2007 CrystalClear Software, Inc.
5 * Use, modification and distribution is subject to the
6 * Boost Software License, Version 1.0. (See accompanying
7 * file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
8 * Author: Jeff Garland, Bart Garst
9 * $Date$
10 */
11
12/*! @file dst_rules.hpp
13 Contains template class to provide static dst rule calculations
14*/
15
16#include "boost/date_time/date_generators.hpp"
17#include "boost/date_time/period.hpp"
18#include "boost/date_time/date_defs.hpp"
19#include <stdexcept>
20
21namespace boost {
22 namespace date_time {
23
24 enum time_is_dst_result {is_not_in_dst, is_in_dst,
25 ambiguous, invalid_time_label};
26
27
28 //! Dynamic class used to caluclate dst transition information
29 template<class date_type_,
30 class time_duration_type_>
31 class dst_calculator
32 {
33 public:
34 typedef time_duration_type_ time_duration_type;
35 typedef date_type_ date_type;
36
37 //! Check the local time offset when on dst start day
38 /*! On this dst transition, the time label between
39 * the transition boundary and the boudary + the offset
40 * are invalid times. If before the boundary then still
41 * not in dst.
42 *@param time_of_day Time offset in the day for the local time
43 *@param dst_start_offset_minutes Local day offset for start of dst
44 *@param dst_length_minutes Number of minutes to adjust clock forward
45 *@retval status of time label w.r.t. dst
46 */
47 static time_is_dst_result
48 process_local_dst_start_day(const time_duration_type& time_of_day,
49 unsigned int dst_start_offset_minutes,
50 long dst_length_minutes)
51 {
52 //std::cout << "here" << std::endl;
53 if (time_of_day < time_duration_type(0,dst_start_offset_minutes,0)) {
54 return is_not_in_dst;
55 }
56 long offset = dst_start_offset_minutes + dst_length_minutes;
57 if (time_of_day >= time_duration_type(0,offset,0)) {
58 return is_in_dst;
59 }
60 return invalid_time_label;
61 }
62
63 //! Check the local time offset when on the last day of dst
64 /*! This is the calculation for the DST end day. On that day times
65 * prior to the conversion time - dst_length (1 am in US) are still
66 * in dst. Times between the above and the switch time are
67 * ambiguous. Times after the start_offset are not in dst.
68 *@param time_of_day Time offset in the day for the local time
69 *@param dst_end_offset_minutes Local time of day for end of dst
70 *@retval status of time label w.r.t. dst
71 */
72 static time_is_dst_result
73 process_local_dst_end_day(const time_duration_type& time_of_day,
74 unsigned int dst_end_offset_minutes,
75 long dst_length_minutes)
76 {
77 //in US this will be 60 so offset in day is 1,0,0
78 int offset = dst_end_offset_minutes-dst_length_minutes;
79 if (time_of_day < time_duration_type(0,offset,0)) {
80 return is_in_dst;
81 }
82 if (time_of_day >= time_duration_type(0,dst_end_offset_minutes,0)) {
83 return is_not_in_dst;
84 }
85 return ambiguous;
86 }
87
88 //! Calculates if the given local time is dst or not
89 /*! Determines if the time is really in DST or not. Also checks for
90 * invalid and ambiguous.
91 * @param current_day The day to check for dst
92 * @param time_of_day Time offset within the day to check
93 * @param dst_start_day Starting day of dst for the given locality
94 * @param dst_start_offset Time offset within day for dst boundary
95 * @param dst_end_day Ending day of dst for the given locality
96 * @param dst_end_offset Time offset within day given in dst for dst boundary
97 * @param dst_length lenght of dst adjusment
98 * @retval The time is either ambiguous, invalid, in dst, or not in dst
99 */
100 static time_is_dst_result
101 local_is_dst(const date_type& current_day,
102 const time_duration_type& time_of_day,
103 const date_type& dst_start_day,
104 const time_duration_type& dst_start_offset,
105 const date_type& dst_end_day,
106 const time_duration_type& dst_end_offset,
107 const time_duration_type& dst_length_minutes)
108 {
109 unsigned int start_minutes =
110 dst_start_offset.hours() * 60 + dst_start_offset.minutes();
111 unsigned int end_minutes =
112 dst_end_offset.hours() * 60 + dst_end_offset.minutes();
113 long length_minutes =
114 dst_length_minutes.hours() * 60 + dst_length_minutes.minutes();
115
116 return local_is_dst(current_day, time_of_day,
117 dst_start_day, start_minutes,
118 dst_end_day, end_minutes,
119 length_minutes);
120 }
121
122 //! Calculates if the given local time is dst or not
123 /*! Determines if the time is really in DST or not. Also checks for
124 * invalid and ambiguous.
125 * @param current_day The day to check for dst
126 * @param time_of_day Time offset within the day to check
127 * @param dst_start_day Starting day of dst for the given locality
128 * @param dst_start_offset_minutes Offset within day for dst
129 * boundary (eg 120 for US which is 02:00:00)
130 * @param dst_end_day Ending day of dst for the given locality
131 * @param dst_end_offset_minutes Offset within day given in dst for dst
132 * boundary (eg 120 for US which is 02:00:00)
133 * @param dst_length_minutes Length of dst adjusment (eg: 60 for US)
134 * @retval The time is either ambiguous, invalid, in dst, or not in dst
135 */
136 static time_is_dst_result
137 local_is_dst(const date_type& current_day,
138 const time_duration_type& time_of_day,
139 const date_type& dst_start_day,
140 unsigned int dst_start_offset_minutes,
141 const date_type& dst_end_day,
142 unsigned int dst_end_offset_minutes,
143 long dst_length_minutes)
144 {
145 //in northern hemisphere dst is in the middle of the year
146 if (dst_start_day < dst_end_day) {
147 if ((current_day > dst_start_day) && (current_day < dst_end_day)) {
148 return is_in_dst;
149 }
150 if ((current_day < dst_start_day) || (current_day > dst_end_day)) {
151 return is_not_in_dst;
152 }
153 }
154 else {//southern hemisphere dst is at begining /end of year
155 if ((current_day < dst_start_day) && (current_day > dst_end_day)) {
156 return is_not_in_dst;
157 }
158 if ((current_day > dst_start_day) || (current_day < dst_end_day)) {
159 return is_in_dst;
160 }
161 }
162
163 if (current_day == dst_start_day) {
164 return process_local_dst_start_day(time_of_day,
165 dst_start_offset_minutes,
166 dst_length_minutes);
167 }
168
169 if (current_day == dst_end_day) {
170 return process_local_dst_end_day(time_of_day,
171 dst_end_offset_minutes,
172 dst_length_minutes);
173 }
174 //you should never reach this statement
175 return invalid_time_label;
176 }
177
178 };
179
180
181 //! Compile-time configurable daylight savings time calculation engine
182 /* This template provides the ability to configure a daylight savings
183 * calculation at compile time covering all the cases. Unfortunately
184 * because of the number of dimensions related to daylight savings
185 * calculation the number of parameters is high. In addition, the
186 * start and end transition rules are complex types that specify
187 * an algorithm for calculation of the starting day and ending
188 * day of daylight savings time including the month and day
189 * specifications (eg: last sunday in October).
190 *
191 * @param date_type A type that represents dates, typically gregorian::date
192 * @param time_duration_type Used for the offset in the day calculations
193 * @param dst_traits A set of traits that define the rules of dst
194 * calculation. The dst_trait must include the following:
195 * start_rule_functor - Rule to calculate the starting date of a
196 * dst transition (eg: last_kday_of_month).
197 * start_day - static function that returns month of dst start for
198 * start_rule_functor
199 * start_month -static function that returns day or day of week for
200 * dst start of dst
201 * end_rule_functor - Rule to calculate the end of dst day.
202 * end_day - static fucntion that returns end day for end_rule_functor
203 * end_month - static function that returns end month for end_rule_functor
204 * dst_start_offset_minutes - number of minutes from start of day to transition to dst -- 120 (or 2:00 am) is typical for the U.S. and E.U.
205 * dst_start_offset_minutes - number of minutes from start of day to transition off of dst -- 180 (or 3:00 am) is typical for E.U.
206 * dst_length_minutes - number of minutes that dst shifts clock
207 */
208 template<class date_type,
209 class time_duration_type,
210 class dst_traits>
211 class dst_calc_engine
212 {
213 public:
214 typedef typename date_type::year_type year_type;
215 typedef typename date_type::calendar_type calendar_type;
216 typedef dst_calculator<date_type, time_duration_type> dstcalc;
217
218 //! Calculates if the given local time is dst or not
219 /*! Determines if the time is really in DST or not. Also checks for
220 * invalid and ambiguous.
221 * @retval The time is either ambiguous, invalid, in dst, or not in dst
222 */
223 static time_is_dst_result local_is_dst(const date_type& d,
224 const time_duration_type& td)
225 {
226
227 year_type y = d.year();
228 date_type dst_start = local_dst_start_day(y);
229 date_type dst_end = local_dst_end_day(y);
230 return dstcalc::local_is_dst(d,td,
231 dst_start,
232 dst_traits::dst_start_offset_minutes(),
233 dst_end,
234 dst_traits::dst_end_offset_minutes(),
235 dst_traits::dst_shift_length_minutes());
236
237 }
238
239 static bool is_dst_boundary_day(date_type d)
240 {
241 year_type y = d.year();
242 return ((d == local_dst_start_day(y)) ||
243 (d == local_dst_end_day(y)));
244 }
245
246 //! The time of day for the dst transition (eg: typically 01:00:00 or 02:00:00)
247 static time_duration_type dst_offset()
248 {
249 return time_duration_type(0,dst_traits::dst_shift_length_minutes(),0);
250 }
251
252 static date_type local_dst_start_day(year_type year)
253 {
254 return dst_traits::local_dst_start_day(year);
255 }
256
257 static date_type local_dst_end_day(year_type year)
258 {
259 return dst_traits::local_dst_end_day(year);
260 }
261
262
263 };
264
265 //! Depricated: Class to calculate dst boundaries for US time zones
266 /* Use dst_calc_engine instead.
267 * In 2007 US/Canada DST rules changed
268 * (http://en.wikipedia.org/wiki/Energy_Policy_Act_of_2005#Change_to_daylight_saving_time).
269 */
270 template<class date_type_,
271 class time_duration_type_,
272 unsigned int dst_start_offset_minutes=120, //from start of day
273 short dst_length_minutes=60> //1 hour == 60 min in US
274 class us_dst_rules
275 {
276 public:
277 typedef time_duration_type_ time_duration_type;
278 typedef date_type_ date_type;
279 typedef typename date_type::year_type year_type;
280 typedef typename date_type::calendar_type calendar_type;
281 typedef date_time::last_kday_of_month<date_type> lkday;
282 typedef date_time::first_kday_of_month<date_type> fkday;
283 typedef date_time::nth_kday_of_month<date_type> nkday;
284 typedef dst_calculator<date_type, time_duration_type> dstcalc;
285
286 //! Calculates if the given local time is dst or not
287 /*! Determines if the time is really in DST or not. Also checks for
288 * invalid and ambiguous.
289 * @retval The time is either ambiguous, invalid, in dst, or not in dst
290 */
291 static time_is_dst_result local_is_dst(const date_type& d,
292 const time_duration_type& td)
293 {
294
295 year_type y = d.year();
296 date_type dst_start = local_dst_start_day(y);
297 date_type dst_end = local_dst_end_day(y);
298 return dstcalc::local_is_dst(d,td,
299 dst_start,dst_start_offset_minutes,
300 dst_end, dst_start_offset_minutes,
301 dst_length_minutes);
302
303 }
304
305
306 static bool is_dst_boundary_day(date_type d)
307 {
308 year_type y = d.year();
309 return ((d == local_dst_start_day(y)) ||
310 (d == local_dst_end_day(y)));
311 }
312
313 static date_type local_dst_start_day(year_type year)
314 {
315 if (year >= year_type(2007)) {
316 //second sunday in march
317 nkday ssim(nkday::second, Sunday, gregorian::Mar);
318 return ssim.get_date(year);
319 } else {
320 //first sunday in april
321 fkday fsia(Sunday, gregorian::Apr);
322 return fsia.get_date(year);
323 }
324 }
325
326 static date_type local_dst_end_day(year_type year)
327 {
328 if (year >= year_type(2007)) {
329 //first sunday in november
330 fkday fsin(Sunday, gregorian::Nov);
331 return fsin.get_date(year);
332 } else {
333 //last sunday in october
334 lkday lsio(Sunday, gregorian::Oct);
335 return lsio.get_date(year);
336 }
337 }
338
339 static time_duration_type dst_offset()
340 {
341 return time_duration_type(0,dst_length_minutes,0);
342 }
343
344 private:
345
346
347 };
348
349 //! Used for local time adjustments in places that don't use dst
350 template<class date_type_, class time_duration_type_>
351 class null_dst_rules
352 {
353 public:
354 typedef time_duration_type_ time_duration_type;
355 typedef date_type_ date_type;
356
357
358 //! Calculates if the given local time is dst or not
359 /*! @retval Always is_not_in_dst since this is for zones without dst
360 */
361 static time_is_dst_result local_is_dst(const date_type&,
362 const time_duration_type&)
363 {
364 return is_not_in_dst;
365 }
366
367 //! Calculates if the given utc time is in dst
368 static time_is_dst_result utc_is_dst(const date_type&,
369 const time_duration_type&)
370 {
371 return is_not_in_dst;
372 }
373
374 static bool is_dst_boundary_day(date_type /*d*/)
375 {
376 return false;
377 }
378
379 static time_duration_type dst_offset()
380 {
381 return time_duration_type(0,0,0);
382 }
383
384 };
385
386
387 } } //namespace date_time
388
389
390
391#endif
392