1<?xml version="1.0" encoding="utf-8"?> 2<!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN" 3"../../../tools/boostbook/dtd/boostbook.dtd"> 4 5<!-- Copyright (c) 2001-2005 CrystalClear Software, Inc. 6 Subject to the Boost Software License, Version 1.0. 7 (See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt) 8--> 9 10<section id="date_time.local_time.local_date_time"> 11 <title>Local Date Time</title> 12 13 <link linkend="local_date_time_intro">Introduction</link> -- 14 <link linkend="local_date_time_header">Header</link> -- 15 <link linkend="local_date_time_clock_constr">Construct From Clock</link> -- 16 <link linkend="local_date_time_constr">Construction</link> -- 17 <link linkend="local_date_time_accessors">Accessors</link> -- 18 <link linkend="local_date_time_operators">Operators</link> -- 19 <link linkend="local_date_time_tm_func">Struct tm Functions</link> 20 21 <anchor id="local_date_time_intro" /> 22 <bridgehead renderas="sect3">Introduction</bridgehead> 23 <para> 24 A local_date_time object is a point in time and an associated time zone. The time is represented internally as UTC. 25 </para> 26 27 <anchor id="local_date_time_header" /> 28 <bridgehead renderas="sect3">Header</bridgehead> 29 <para> 30 The inclusion of a single header will bring in all boost::local_time types, 31functions, and IO operators. 32 <programlisting> 33 #include "boost/date_time/local_time/local_time.hpp" 34 </programlisting> 35 </para> 36 37 <anchor id="local_date_time_clock_constr" /> 38 <bridgehead renderas="sect3">Construct From Clock</bridgehead> 39 <para> 40 Creation of a local_date_time object from clock is possible with either second, or sub second resolution. 41 </para> 42 <para> 43 <informaltable frame="all"> 44 <tgroup cols="2"> 45 <thead> 46 <row> 47 <entry>Syntax</entry> 48 <entry>Example</entry> 49 </row> 50 </thead> 51 <tbody> 52 <row> 53 <entry valign="top"><screen>local_microsec_clock(...) 54 Return Type: 55 local_date_time 56 Parameter: 57 time_zone_ptr</screen></entry> 58 <entry><screen>time_zone_ptr zone( 59 new posix_time_zone("MST-07") 60); 61local_date_time ldt = 62 local_microsec_clock::local_time( 63 zone);</screen> 64 </entry> 65 </row> 66 <row> 67 <entry valign="top"><screen>local_sec_clock(...) 68 Return Type: 69 local_date_time 70 Parameter: 71 time_zone_ptr</screen></entry> 72 <entry><screen>time_zone_ptr zone( 73 new posix_time_zone("MST-07") 74); 75local_date_time ldt = 76 local_sec_clock::local_time(zone);</screen> 77 </entry> 78 </row> 79 </tbody> 80 </tgroup> 81 </informaltable> 82 </para> 83 84 <anchor id="local_date_time_constr" /> 85 <bridgehead renderas="sect3">Construction</bridgehead> 86 <para> 87 Construction of a local_date_time object can be done with a ptime and a time_zone_ptr where the ptime represents UTC time. Construction with a wall-clock representation takes the form of a date, a time_duration, a time_zone_ptr, and a fourth parameter that addresses the following complication. 88 </para> 89 <para> 90 Construction from a wall-clock rep may result in differing shifts for a particular time zone, depending on daylight savings rules for that zone. This means it is also possible to create a local_date_time with a non-existent, or duplicated, UTC representation. These cases occur during the forward shift in time that is the transition into daylight savings and during the backward shift that is the transition out of daylight savings. The user has two options for handling these cases: a bool flag that states if the time is daylight savings, or an enum that states what to do when either of these cases are encountered. 91 </para> 92 <para> 93 The bool flag is ignored when the given time_zone has no daylight savings specification. When the daylight savings status of a given time label is calculated and it does not match the flag, a <code>local_time::dst_not_valid</code> exception is thrown. If a time label is invalid (does not exist), a <code>local_time::time_label_invalid</code> exception is thrown. 94 </para> 95 <para> 96 There are two elements in the <code>local_date_time::DST_CALC_OPTIONS</code> enum: <code>EXCEPTION_ON_ERROR</code> and <code>NOT_DATE_TIME_ON_ERROR</code>. The possible exceptions thrown are a <code>local_time::ambiguous_result</code> or a <code>local_time::time_label_invalid</code>. The <code>NOT_DATE_TIME_ON_ERROR</code> sets the time value to the special value <code>local_time::not_a_date_time</code> in the event of either a invalid or an ambiguous time label. 97 </para> 98 <para> 99 <informaltable frame="all"> 100 <tgroup cols="2"> 101 <thead> 102 <row> 103 <entry morerows="1">Syntax</entry> 104 <entry>Description</entry> 105 </row> 106 <row> 107 <entry>Example</entry> 108 </row> 109 </thead> 110 <tbody> 111 <row> 112 <entry valign="top" morerows="1"><screen>local_date_time(...) 113 Parameters: 114 posix_time::ptime 115 time_zone_ptr</screen></entry> 116 <entry>The given time is expected to be UTC. Therefore, the given time will be adjusted according to the offset described in the time zone.</entry> 117 </row> 118 <row> 119 <entry><screen> 120// 3am, 2004-Nov-05 local time 121ptime pt(date(2004,Nov,5), 122 hours(10)); 123time_zone_ptr zone( 124 new posix_time_zone("MST-07")); 125local_date_time az(pt, zone);</screen> 126 </entry> 127 </row> 128 129 <row> 130 <entry valign="top" morerows="1"><screen>local_date_time(...) 131 Parameters: 132 date 133 time_duration 134 time_zone_ptr 135 bool</screen></entry> 136<entry>The passed time information understood to be in the passed tz. The DST flag must be passed to indicate whether the time is in daylight savings or not. May throw a <code>dst_not_valid</code> or <code>time_label_invalid</code> exception.</entry> 137 </row> 138 <row> 139 <entry><screen>date d(2004,Nov,5); 140time_duration td(5,0,0,0); 141string z("PST-8PDT,M4.1.0,M10.1.0") 142time_zone_ptr zone( 143 new posix_time_zone(z)); 144local_date_time nyc(d, td, 145 zone, false);</screen> 146 </entry> 147 </row> 148 149 <row> 150 <entry valign="top" morerows="1"><screen>local_date_time(...) 151 Parameters: 152 date 153 time_duration 154 time_zone_ptr 155 DST_CALC_OPTIONS</screen></entry> 156 <entry>The passed time information understood to be in the passed tz. The DST flag is calculated according to the specified rule. May throw a <code>ambiguous_result</code> or <code>time_label_invalid</code> exception.</entry> 157 </row> 158 <row> 159 <entry><screen>date d(2004,Nov,5); 160time_duration td(5,0,0,0); 161string z("PST-8PDT,M4.1.0,M10.1.0") 162time_zone_ptr zone( 163 new posix_time_zone(z)); 164local_date_time nyc(d, td, zone, 165 NOT_DATE_TIME_ON_ERROR);</screen> 166 </entry> 167 </row> 168 169 <row> 170 <entry valign="top" morerows="1"><screen>local_date_time(local_date_time);</screen></entry> 171 <entry>Copy Constructor.</entry> 172 </row> 173 <row> 174 <entry><screen>local_date_time az_2(az);</screen></entry> 175 </row> 176 177 <row> 178 <entry valign="top" morerows="1"><screen>local_date_time(...) 179 Parameters: 180 special_values 181 time_zone_ptr</screen></entry> 182 <entry>Special Values constructor.</entry> 183 </row> 184 <row> 185 <entry><screen>time_zone_ptr zone( 186 new posix_time_zone("MST-07") 187); 188local_date_time nadt(not_a_date_time, 189 zone); 190// default NULL time_zone_ptr 191local_date_time nadt(pos_infin);</screen> 192 </entry> 193 </row> 194 195 </tbody> 196 </tgroup> 197 </informaltable> 198 </para> 199 200 <anchor id="local_date_time_accessors" /> 201 <bridgehead renderas="sect3">Accessors</bridgehead> 202 <para> 203 <informaltable frame="all"> 204 <tgroup cols="2"> 205 <thead> 206 <row> 207 <entry valign="top" morerows="1">Syntax</entry> 208 <entry>Description</entry> 209 </row> 210 <row> 211 <entry>Example</entry> 212 </row> 213 </thead> 214 <tbody> 215 <row> 216 <entry valign="top" morerows="1"><screen>time_zone_ptr zone()</screen></entry> 217 <entry>Returns associated time_zone object via a time_zone_ptr</entry> 218 </row> 219 <row> 220 <entry><screen></screen></entry> 221 </row> 222 223 <row> 224 <entry valign="top" morerows="1"><screen>bool is_dst()</screen></entry> 225 <entry>Determines if time value is in DST for associated zone.</entry> 226 </row> 227 <row> 228 <entry></entry> 229 </row> 230 231 <row> 232 <entry valign="top" morerows="1"><screen>ptime utc_time()</screen></entry> 233 <entry>Converts the local time value to a UTC value.</entry> 234 </row> 235 <row> 236 <entry><screen>ptime pt(date(2004,Nov,5), 237 hours(10)); 238time_zone_ptr zone( 239 new posix_time_zone("MST-07")); 240local_date_time az(pt, zone); 241az.utc_time(); // 10am 2004-Nov-5</screen> 242 </entry> 243 </row> 244 245 <row> 246 <entry valign="top" morerows="1"><screen>ptime local_time()</screen></entry> 247 <entry>Returns the local time for this object (Wall-clock).</entry> 248 </row> 249 <row> 250 <entry><screen>ptime pt(date(2004,Nov,5), 251 hours(10)); 252time_zone_ptr zone( 253 new posix_time_zone("MST-07")); 254local_date_time az(pt, zone); 255az.utc_time(); // 10am 2004-Nov-5 256az.local_time(); // 3am 2004-Nov-5</screen></entry> 257 </row> 258 259 <row> 260 <entry valign="top" morerows="1"><screen>local_time_in(...) 261 Return Type: 262 local_date_time 263 Parameters: 264 time_zone_ptr 265 time_duration</screen></entry> 266 <entry>Returns a local_date_time representing the same UTC time as calling object, plus optional time_duration, with given time zone.</entry> 267 </row> 268 <row> 269 <entry><screen>local_date_time nyc = az.local_time_in(nyc_zone); 270// nyc == 7am 2004-Nov-5</screen> 271 </entry> 272 </row> 273 <!-- 274 <row> 275 <entry valign="top" morerows="1"><screen>std::string zone_name()</screen></entry> 276 <entry>Returns full zone name from associated time zone or "Coordinated Universal Time" if time_zone_ptr is NULL.</entry> 277 </row> 278 <row> 279 <entry> 280 </entry> 281 </row> 282 283 <row> 284 <entry valign="top" morerows="1"><screen>std::string zone_abbrev()</screen></entry> 285 <entry>Returns zone abbreviation from associated time zone or "UTC" if time_zone_ptr is NULL.</entry> 286 </row> 287 <row> 288 <entry> 289 </entry> 290 </row> 291 --> 292 <row> 293 <entry valign="top" morerows="1"><screen>bool is_infinity() const</screen></entry> 294 <entry>Returns true if local_date_time is either positive or negative infinity</entry> 295 </row> 296 <row> 297 <entry><screen>local_date_time ldt(pos_infin); 298ldt.is_infinity(); // --> true</screen></entry> 299 </row> 300 301 <row> 302 <entry valign="top" morerows="1"><screen>bool is_neg_infinity() const</screen></entry> 303 <entry>Returns true if local_date_time is negative infinity</entry> 304 </row> 305 <row> 306 <entry><screen>local_date_time ldt(neg_infin); 307ldt.is_neg_infinity(); // --> true</screen></entry> 308 </row> 309 310 <row> 311 <entry valign="top" morerows="1"><screen>bool is_pos_infinity() const</screen></entry> 312 <entry>Returns true if local_date_time is positive infinity</entry> 313 </row> 314 <row> 315 <entry><screen>local_date_time ldt(neg_infin); 316ldt.is_pos_infinity(); // --> true</screen></entry> 317 </row> 318 319 <row> 320 <entry valign="top" morerows="1"><screen>bool is_not_a_date_time() const</screen></entry> 321 <entry>Returns true if value is not a date</entry> 322 </row> 323 <row> 324 <entry><screen>local_date_time ldt(not_a_date_time); 325ldt.is_not_a_date_time(); // --> true</screen></entry> 326 </row> 327 328 <row> 329 <entry valign="top" morerows="1"><screen>bool is_special() const</screen></entry> 330 <entry>Returns true if local_date_time is any <code>special_value</code></entry> 331 </row> 332 <row> 333 <entry><screen>local_date_time ldt(pos_infin); 334local_date_time ldt2(not_a_date_time); 335time_zone_ptr 336 mst(new posix_time_zone("MST-07")); 337local_date_time 338 ldt3(local_sec_clock::local_time(mst)); 339ldt.is_special(); // --> true 340ldt2.is_special(); // --> true 341ldt3.is_special(); // --> false</screen></entry> 342 </row> 343 344 </tbody> 345 </tgroup> 346 </informaltable> 347 </para> 348 349 <anchor id="local_date_time_operators" /> 350 <bridgehead renderas="sect3">Operators</bridgehead> 351 <informaltable frame="all"> 352 <tgroup cols="2"> 353 <thead> 354 <row> 355 <entry valign="top" morerows="1">Syntax</entry> 356 <entry>Description</entry> 357 </row> 358 <row> 359 <entry>Example</entry> 360 </row> 361 </thead> 362 <tbody> 363 <row> 364 <entry valign="top" morerows="1"><screen>operator<<</screen></entry> 365 <entry>Output streaming operator. This operator is part of the v1.33 IO addition to date_time. For complete details on this feature see <link linkend="date_time.date_time_io">Date Time IO</link>. The default output is shown in this example.</entry> 366 </row> 367 <row> 368 <entry><screen> 369time_zone_ptr zone(new posix_time_zone("MST-07"); 370local_date_time ldt(date(2005,Jul,4), 371 hours(20), 372 false); 373std::cout << ldt << std::endl; 374// "2005-Jul-04 20:00:00 MST" 375 </screen></entry> 376 </row> 377 378 <row> 379 <entry valign="top" morerows="1"><screen>operator>></screen></entry> 380 <entry>Input streaming operator. This operator is part of the v1.33 IO addition to date_time. For complete details on this feature see <link linkend="date_time.date_time_io">Date Time IO</link>. At this time, <code>local_date_time</code> objects can only be streamed in with a Posix Time Zone string. A complete description of a Posix Time Zone string can be found in the documentation for the <link linkend="posix_time_zone_intro">posix_time_zone</link> class.</entry> 381 </row> 382 <row> 383 <entry><screen>stringstream ss; 384ss.str("2005-Jul-04 20:00:00 MST-07"); 385ss >> ldt; 386 </screen></entry> 387 </row> 388 389 <row> 390 <entry valign="top" morerows="1"><screen>operator==, operator!=, 391operator>, operator<, 392operator>=, operator<=</screen></entry> 393 <entry>A full complement of comparison operators</entry> 394 </row> 395 <row> 396 <entry><screen>ldt1 == ldt2, etc</screen></entry> 397 </row> 398 399 <row> 400 <entry valign="top" morerows="1"><screen>operator+, operator+=, 401operator-, operator-=</screen></entry> 402 <entry>Addition, subtraction, and shortcut operators for <code>local_date_time</code> and date duration types. These include: <code>days</code>, <code>months</code>, and <code>years</code>.</entry> 403 </row> 404 <row> 405 <entry><screen>ldt + days(5), etc</screen></entry> 406 </row> 407 408 <row> 409 <entry valign="top" morerows="1"><screen>operator+, operator+=, 410operator-, operator-=</screen></entry> 411 <entry>Addition, subtraction, and shortcut operators for <code>local_date_time</code> and <code>time_duration</code>.</entry> 412 </row> 413 <row> 414 <entry><screen>ldt + hours(5), etc</screen></entry> 415 </row> 416 </tbody> 417 </tgroup> 418 </informaltable> 419 420 <anchor id="local_date_time_tm_func" /> 421 <bridgehead renderas="sect3">Struct tm Functions</bridgehead> 422 <para>Function for converting a <code>local_date_time</code> object to a <code>tm</code> struct is provided.</para> 423 <informaltable frame="all"> 424 <tgroup cols="2"> 425 <thead> 426 <row> 427 <entry valign="top" morerows="1">Syntax</entry> 428 <entry>Description</entry> 429 </row> 430 <row> 431 <entry>Example</entry> 432 </row> 433 </thead> 434 <tbody> 435 <row> 436 <entry valign="top" morerows="1"><screen>tm to_tm(local_date_time)</screen></entry> 437 <entry>A function for converting a <code>local_date_time</code> object to a <code>tm</code> struct.</entry> 438 </row> 439 <row> 440 <entry><screen> 441// 6am, 2005-Jul-05 local time 442std::string z("EST-05EDT,M4.1.0,M10.1.0"); 443ptime pt(date(2005,Jul,5), 444 hours(10)); 445time_zone_ptr zone( new posix_time_zone(z)); 446local_date_time ldt(pt, zone); 447tm ldt_tm = to_tm(ldt); 448/* tm_year => 105 449 tm_mon => 6 450 tm_mday => 5 451 tm_wday => 2 (Tuesday) 452 tm_yday => 185 453 tm_hour => 6 454 tm_min => 0 455 tm_sec => 0 456 tm_isdst => 1 */</screen> 457 </entry> 458 </row> 459 460 </tbody> 461 </tgroup> 462 </informaltable> 463</section> 464