Introduction -- Header -- Construction -- Construct from String -- Construct from Clock -- Accessors -- Convert to String -- Operators -- Struct tm Functions Introduction The class boost::gregorian::date is the primary interface for date programming. In general, the date class is immutable once constructed although it does allow assignment from another date. Techniques for creating dates include reading the current date from the clock, using date iterators, and date algorithms or generators. Internally boost::gregorian::date is stored as a 32 bit integer type. The class is specifically designed to NOT contain virtual functions. This design allows for efficient calculation and memory usage with large collections of dates. The construction of a date validates all input so that it is not possible to construct an 'invalid' date. That is 2001-Feb-29 cannot be constructed as a date. Various exceptions derived from std::out_of_range are thrown to indicate which aspect of the date input is invalid. Note that the special value not-a-date-time can be used as 'invalid' or 'null' date if so desired. Header #include "boost/date_time/gregorian/gregorian.hpp" //include all types plus i/o or #include "boost/date_time/gregorian/gregorian_types.hpp" //no i/o just types Construction Syntax Description Example date(greg_year, greg_month, greg_day) Construct from parts of date. Throws bad_year, bad_day_of_month, or bad_day_month (derivatives of std::out_of_range) if the year, month or day are out of range. date d(2002,Jan,10); date(date d) Copy constructor date d1(d); date(special_values sv) Constructor for infinities, not-a-date-time, max_date_time, and min_date_time date d1(neg_infin); date d2(pos_infin); date d3(not_a_date_time); date d4(max_date_time); date d5(min_date_time); date() Default constructor. Creates a date object initialized to not_a_date_time. NOTE: this constructor can be disabled by defining DATE_TIME_NO_DEFAULT_CONSTRUCTOR (see compiler_config.hpp) date d; // d => not_a_date_time Construct from String Syntax Description Example date from_string(std::string) From delimited date string where with order year-month-day eg: 2002-1-25 std::string ds("2002/1/25"); date d(from_string(ds)); date from_undelimited_string(std::string) From iso type date string where with order year-month-day eg: 20020125 std::string ds("20020125"); date d(from_undelimited_string(ds)); Construct from Clock Syntax Description Example day_clock::local_day() Get the local day based on the time zone settings of the computer. date d(day_clock::local_day()); day_clock::universal_day() Get the UTC day. date d(day_clock::universal_day()); Accessors Syntax Description Example greg_year year() const Get the year part of the date. date d(2002,Jan,10); d.year(); // --> 2002 greg_month month() const Get the month part of the date. date d(2002,Jan,10); d.month(); // --> 1 greg_day day() const Get the day part of the date. date d(2002,Jan,10); d.day(); // --> 10 greg_ymd year_month_day() const Return a year_month_day struct. More efficient when all 3 parts of the date are needed. date d(2002,Jan,10); date::ymd_type ymd = d.year_month_day(); // ymd.year --> 2002, // ymd.month --> 1, // ymd.day --> 10 greg_day_of_week day_of_week() const Get the day of the week (Sunday, Monday, etc.) date d(2002,Jan,10); d.day_of_week(); // --> Thursday greg_day_of_year day_of_year() const Get the day of the year. Number from 1 to 366 date d(2000,Jan,10); d.day_of_year(); // --> 10 date end_of_month() const Returns a date object set to the last day of the calling objects current month. date d(2000,Jan,10); d.end_of_month(); // --> 2000-Jan-31 bool is_infinity() const Returns true if date is either positive or negative infinity date d(pos_infin); d.is_infinity(); // --> true bool is_neg_infinity() const Returns true if date is negative infinity date d(neg_infin); d.is_neg_infinity(); // --> true bool is_pos_infinity() const Returns true if date is positive infinity date d(pos_infin); d.is_pos_infinity(); // --> true bool is_not_a_date() const Returns true if value is not a date date d(not_a_date_time); d.is_not_a_date(); // --> true bool is_special() const Returns true if date is any special_value date d(pos_infin); date d2(not_a_date_time); date d3(2005,Mar,1); d.is_special(); // --> true d2.is_special(); // --> true d3.is_special(); // --> false special_value as_special() const Returns represented special_value or not_special if the represented date is a normal date. long modjulian_day() const Returns the modified julian day for the date. long julian_day() const Returns the julian day for the date. int week_number() const Returns the ISO 8601 week number for the date. date end_of_month() const Returns the last day of the month for the date. date d(2000,Feb,1); //gets Feb 29 -- 2000 was leap year date eom = d.end_of_month(); Convert to String Syntax Description Example std::string to_simple_string(date d) To YYYY-mmm-DD string where mmm is a 3 char month name. "2002-Jan-01" std::string to_iso_string(date d) To YYYYMMDD where all components are integers. "20020131" std::string to_iso_extended_string(date d) To YYYY-MM-DD where all components are integers. "2002-01-31" Operators Syntax Description Example operator<< Stream output operator date d(2002,Jan,1); std::cout << d << std::endl; operator>> Stream input operator. Note: As of version 1.33, streaming operations have been greatly improved. See Date Time IO System for details on exceptions and error conditions. date d(not_a_date_time); stringstream ss("2002-Jan-01"); ss >> d; operator==, operator!=, operator>, operator<, operator>=, operator<= A full complement of comparison operators d1 == d2, etc date operator+(date_duration) const Return a date adding a day offset date d(2002,Jan,1); date_duration dd(1); date d2 = d + dd; date operator-(date_duration) const Return a date by substracting a day offset date d(2002,Jan,1); date_duration dd(1); date d2 = d - dd; date_duration operator-(date) const Return a date_duration by subtracting two dates date d1(2002,Jan,1); date d2(2002,Jan,2); date_duration dd = d2-d1; Struct tm Functions Functions for converting a date object to, and from, a tm struct are provided. Syntax Description Example tm to_tm(date) A function for converting a date object to a tm struct. The fields: tm_hour, tm_min, and tm_sec are set to zero. The tm_isdst field is set to -1. date d(2005,Jan,1); tm d_tm = to_tm(d); /* tm_year => 105 tm_mon => 0 tm_mday => 1 tm_wday => 6 (Saturday) tm_yday => 0 tm_hour => 0 tm_min => 0 tm_sec => 0 tm_isddst => -1 */ date date_from_tm(tm datetm) A function for converting a tm struct to a date object. The fields: tm_wday , tm_yday , tm_hour, tm_min, tm_sec, and tm_isdst are ignored. tm d_tm; d_tm.tm_year = 105; d_tm.tm_mon = 0; d_tm.tm_mday = 1; date d = date_from_tm(d_tm); // d => 2005-Jan-01