date_time/example/local_time/seconds_since_epoch.cpp
Jeff Garland e26fd2ed98
pull develop to master for boost 1.72 (#117)
* Synchronize each miscrosec test to the next second (#109)

* Synchronize each miscrosec test to the next second

The aim is to avoid false positives in test_microsec when the seconds,
minutes or hours change during time read between the second_clock and
the microsec_clock.

* Improved readability of the microcec_time_clock test

* Improve performance of adding and subtracting time durations from a ptime. (#99)

Modifying ptime objects by adding and subtracting time durations was
inefficient because it extracted the date and time of day and then
re-constructed a ptime using the date and modified time of day.

This can be avoided by using the existing time_system utilities which
perform the operation by adjusting the number of ticks.

Performance is improved by a factor of 48 on my system.

* Update CI Scripts

* Add time_duration helper functions: (#113)

1. is_positive()
  - Return boolean value to indicate whether or not time duration is
    positive.
2. is_zero()
  - Return boolean value to indicate whether or not time duration is
    zero.
3. abs()
  - Return a time_duration which is the absolute value of time
    duration.

Added documentation for these helper functions and improved existing
documentation to indicate constness, return values or static
functions.

* Cease dependence on MPL (#115)
2019-12-03 17:06:28 -07:00

66 lines
2.2 KiB
C++

/* This example demonstrates the use of the time zone database and
* local time to calculate the number of seconds since the UTC
* time_t epoch 1970-01-01 00:00:00. Note that the selected timezone
* could be any timezone supported in the time zone database file which
* can be modified and updated as needed by the user.
*
* To solve this problem the following steps are required:
* 1) Get a timezone from the tz database for the local time
* 2) Construct a local time using the timezone
* 3) Construct a posix_time::ptime for the time_t epoch time
* 4) Convert the local_time to utc and subtract the epoch time
*
*/
#include "boost/date_time/local_time/local_time.hpp"
#include <iostream>
int main()
{
using namespace boost::gregorian;
using namespace boost::local_time;
using namespace boost::posix_time;
tz_database tz_db;
try {
tz_db.load_from_file("../data/date_time_zonespec.csv");
}catch(const data_not_accessible& dna) {
std::cerr << "Error with time zone data file: " << dna.what() << std::endl;
exit(EXIT_FAILURE);
}catch(const bad_field_count& bfc) {
std::cerr << "Error with time zone data file: " << bfc.what() << std::endl;
exit(EXIT_FAILURE);
}
time_zone_ptr nyc_tz = tz_db.time_zone_from_region("America/New_York");
date in_date(2004,10,04);
time_duration td(12,14,32);
// construct with local time value
// create not-a-date-time if invalid (eg: in dst transition)
local_date_time nyc_time(in_date,
td,
nyc_tz,
local_date_time::NOT_DATE_TIME_ON_ERROR);
std::cout << nyc_time << std::endl;
ptime time_t_epoch(date(1970,1,1));
std::cout << time_t_epoch << std::endl;
// first convert nyc_time to utc via the utc_time()
// call and subtract the ptime.
time_duration diff = nyc_time.utc_time() - time_t_epoch;
//Expected 1096906472
std::cout << "Seconds diff: " << diff.total_seconds() << std::endl;
}
/* Copyright 2005: CrystalClear Software, Inc
* http://www.crystalclearsoftware.com
*
* Subject to the Boost Software License, Version 1.0.
* (See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
*/