Introduction -- Header -- Construction -- Construct from String -- Construct from Clock -- Construct using Conversion functions -- Accessors -- Conversion To String -- Operators -- Struct tm, time_t, and FILETIME Functions Introduction The class boost::posix_time::ptime is the primary interface for time point manipulation. In general, the ptime class is immutable once constructed although it does allow assignment. Class ptime is dependent on gregorian::date for the interface to the date portion of a time point. Other techniques for creating times include time iterators. Header #include "boost/date_time/posix_time/posix_time.hpp" //include all types plus i/o or #include "boost/date_time/posix_time/posix_time_types.hpp" //no i/o just types Construction Syntax Description Example ptime(date,time_duration) Construct from a date and offset ptime t1(date(2002,Jan,10), time_duration(1,2,3)); ptime t2(date(2002,Jan,10), hours(1)+nanosec(5)); ptime(ptime) Copy constructor ptime t3(t1) ptime(special_values sv) Constructor for infinities, not-a-date-time, max_date_time, and min_date_time ptime d1(neg_infin); ptime d2(pos_infin); ptime d3(not_a_date_time); ptime d4(max_date_time); ptime d5(min_date_time); ptime; Default constructor. Creates a ptime object initialized to not_a_date_time. NOTE: this constructor can be disabled by defining DATE_TIME_NO_DEFAULT_CONSTRUCTOR (see compiler_config.hpp) ptime p; // p => not_a_date_time Construct from String Syntax Description Example ptime time_from_string(std::string) From delimited string. NOTE: Excess digits in fractional seconds will be dropped. Ex: "1:02:03.123456999" => 1:02:03.123456. This behavior is affected by the precision the library is compiled with (see Build-Compiler Information. std::string ts("2002-01-20 23:59:59.000"); ptime t(time_from_string(ts)) ptime from_iso_string(std::string) From non delimited iso form string. std::string ts("20020131T235959"); ptime t(from_iso_string(ts)) Construct from Clock Syntax Description Example ptime second_clock::local_time() Get the local time, second level resolution, based on the time zone settings of the computer. ptime t(second_clock::local_time()); ptime second_clock::universal_time() Get the UTC time. ptime t(second_clock::universal_time()) ptime microsec_clock::local_time() Get the local time using a sub second resolution clock. On Unix systems this is implemented using GetTimeOfDay. On most Win32 platforms it is implemented using ftime. Win32 systems often do not achieve microsecond resolution via this API. If higher resolution is critical to your application test your platform to see the achieved resolution. ptime t(microsec_clock::local_time()); ptime microsec_clock::universal_time() Get the UTC time using a sub second resolution clock. On Unix systems this is implemented using GetTimeOfDay. On most Win32 platforms it is implemented using ftime. Win32 systems often do not achieve microsecond resolution via this API. If higher resolution is critical to your application test your platform to see the achieved resolution. ptime t(microsec_clock::universal_time()); Construct using Conversion Functions Syntax Description Example ptime from_time_t(time_t t); Converts a time_t into a ptime. ptime t = from_time_t(tt); ptime from_ftime<ptime>(FILETIME ft); Creates a ptime object from a FILETIME structure. ptime t = from_ftime<ptime>(ft); Accessors Syntax Description Example date date() Get the date part of a time. date d(2002,Jan,10); ptime t(d, hour(1)); t.date() --> 2002-Jan-10; time_duration time_of_day() Get the time offset in the day. date d(2002,Jan,10); ptime t(d, hour(1)); t.time_of_day() --> 01:00:00; bool is_infinity() const Returns true if ptime is either positive or negative infinity ptime pt(pos_infin); pt.is_infinity(); // --> true bool is_neg_infinity() const Returns true if ptime is negative infinity ptime pt(neg_infin); pt.is_neg_infinity(); // --> true bool is_pos_infinity() const Returns true if ptime is positive infinity ptime pt(neg_infin); pt.is_pos_infinity(); // --> true bool is_not_a_date_time() const Returns true if value is not a ptime ptime pt(not_a_date_time); pt.is_not_a_date_time(); // --> true bool is_special() const Returns true if ptime is any special_value ptime pt(pos_infin); ptime pt2(not_a_date_time); ptime pt3(date(2005,Mar,1), hours(10)); pt.is_special(); // --> true pt2.is_special(); // --> true pt3.is_special(); // --> false Conversion to String Syntax Description Example std::string to_simple_string(ptime) To YYYY-mmm-DD HH:MM:SS.fffffffff string where mmm 3 char month name. Fractional seconds only included if non-zero. 2002-Jan-01 10:00:01.123456789 std::string to_iso_string(ptime) Convert to form YYYYMMDDTHHMMSS,fffffffff where T is the date-time separator 20020131T100001,123456789 std::string to_iso_extended_string(ptime) Convert to form YYYY-MM-DDTHH:MM:SS,fffffffff where T is the date-time separator 2002-01-31T10:00:01,123456789 Operators Syntax Description Example operator<<, operator>> Streaming operators. Note: As of version 1.33, streaming operations have been greatly improved. See Date Time IO System for more details (including exceptions and error conditions). ptime pt(not_a_date_time); stringstream ss("2002-Jan-01 14:23:11"); ss >> pt; std::cout << pt; // "2002-Jan-01 14:23:11" operator==, operator!=, operator>, operator<, operator>=, operator<= A full complement of comparison operators t1 == t2, etc ptime operator+(days) Return a ptime adding a day offset date d(2002,Jan,1); ptime t(d,minutes(5)); days dd(1); ptime t2 = t + dd; ptime operator-(days) Return a ptime subtracting a day offset date d(2002,Jan,1); ptime t(d,minutes(5)); days dd(1); ptime t2 = t - dd; ptime operator+(time_duration) Return a ptime adding a time duration date d(2002,Jan,1); ptime t(d,minutes(5)); ptime t2 = t + hours(1) + minutes(2); ptime operator-(time_duration) Return a ptime subtracting a time duration date d(2002,Jan,1); ptime t(d,minutes(5)); ptime t2 = t - minutes(2); time_duration operator-(ptime) Take the difference between two times. date d(2002,Jan,1); ptime t1(d,minutes(5)); ptime t2(d,seconds(5)); time_duration t3 = t2 - t1;//negative result Struct tm, time_t, and FILETIME Functions Functions for converting posix_time objects to, and from, tm structs are provided as well as conversion from time_t and FILETIME. Syntax Description Example tm to_tm(ptime) A function for converting a ptime object to a tm struct. The tm_isdst field is set to -1. ptime pt(date(2005,Jan,1), time_duration(1,2,3)); tm pt_tm = to_tm(pt); /* tm_year => 105 tm_mon => 0 tm_mday => 1 tm_wday => 6 (Saturday) tm_yday => 0 tm_hour => 1 tm_min => 2 tm_sec => 3 tm_isddst => -1 */ ptime ptime_from_tm(tm timetm) A function for converting a tm struct to a ptime object. The fields: tm_wday , tm_yday , and tm_isdst are ignored. tm pt_tm; pt_tm.tm_year = 105; pt_tm.tm_mon = 0; pt_tm.tm_mday = 1; pt_tm.tm_hour = 1; pt_tm.tm_min = 2; pt_tm.tm_sec = 3; ptime pt = ptime_from_tm(pt_tm); // pt => 2005-Jan-01 01:02:03 tm to_tm(time_duration) A function for converting a time_duration object to a tm struct. The fields: tm_year, tm_mon, tm_mday, tm_wday, tm_yday are set to zero. The tm_isdst field is set to -1. time_duration td(1,2,3); tm td_tm = to_tm(td); /* tm_year => 0 tm_mon => 0 tm_mday => 0 tm_wday => 0 tm_yday => 0 tm_hour => 1 tm_min => 2 tm_sec => 3 tm_isddst => -1 */ ptime from_time_t(std::time_t) Creates a ptime from the time_t parameter. The seconds held in the time_t are added to a time point of 1970-Jan-01. ptime pt(not_a_date_time); std::time_t t; t = 1118158776; pt = from_time_t(t); // pt => 2005-Jun-07 15:39:36 ptime from_ftime<ptime>(FILETIME) A template function that constructs a ptime from a FILETIME struct. FILETIME ft; ft.dwHighDateTime = 29715317; ft.dwLowDateTime = 3865122988UL; ptime pt = from_ftime<ptime>(ft); // pt => 2005-Jun-07 15:30:57.039582000