[Boost] Date Constructor

1. Overview
Header file: <boost/date_time.hpp>
This database uses the calendar date system and supports from 1400-Jan-01 to 9999-dec-31.
Class boost: Gregorian: date is the main time type used by the user.
2. Constructor
In date_time, special_values is used to define some special time concepts, including:
Pos_infin (positive infinity)
Neg_infin (negative infinity)
Not_a_date_time (invalid time)
Min_date_time (minimum date or time)
Max_date_time (maximum date or time)
Five is_xxx functions are provided to check whether the date is a special date,
Is_infinity (whether it is an infinite date)
Is_neg_infinity (whether it is a negative infinite date)
Is_pos_infinity (whether it is a positive and infinite date)
Is_not_adate (whether it is an invalid date)
Is_special (whether it is any special date)
3. Example

Void test_dt_construct () {using namespace boost: Gregorian; // 1. common constructor types include date D0; Date D1 (2008, 8, 9); // The most common constructor date D2 (D1 ); // copy and construct date ds1 (neg_infin); Date DS2 (pos_infin); Date DS3 (not_a_date_time); Date DS4 (max_date_time); // 9999-dec-31date ds5 (min_date_time ); // 1400-jan-01assert (d0.is _ not_a_date (); Assert (d0.is _ special (); Assert (ds1.is _ special (); Assert (ds2.is _ special ()); assert (ds3.is _ special () ); Assert (! Ds4.is _ special (); Assert (! Ds5.is _ special (); // 2. use a string to construct date dstr1 (from_string ("2011/08/09"); Date dstr2 (from_string ("2011-08-09"); Date dstr3 (from_string ("2011-feb-28 ")); date dstr4 (from_string ("2011-February-28"); Date dstr5 (from_undelimited_string ("20110809 ")); // The uncommon string date dstr6 (from_us_string ("Feb-28-2011"); // The complete month word can also date dstr7 (from_uk_string ("28-feb-2011 ")); // The complete month word can also be // 3. use clock to construct date DC1 (day_clock: local_day (); Date DC2 (day_clock: universal_day (); // 4. exception during construction try {// year, month, and day will throw an exception when the range is exceeded. date D6 (1300, 12, 25);} catch (STD: exception & E) {STD: cout <E. what () <STD: Endl ;}}