I know you're writing only as an example, but given your notoriety, your source code might actually get used elsewhere.

Please parse the compiled form of the database, after zic is done with it. In doing that, you should also set the default DB path to "/usr/share/zoneinfo", which should work just about anywhere that has a /usr directory.

This should also eliminate the need to set a minimum year to be kept in memory, as the database is already pre-compiled.

This implements reading /usr/share/zone_info tzfiles (issue 1). Because they don't have the same information as the IANA rules I made a couple separate classes tzfile_zone and tzfile_db. I renamed time_zone and TZ_DB to tzrule_zone and tzrule_db respectively, and made typedefs for time_zone and TZ_DB for whatever is specified by TIMEZONE_DEFAULT macro. I renamed zoned_time to basic_zoned_time and it takes a class TimeZone as a template parameter. I also moved things like locate_zone, current_zone, get_tzdb, etc to the _zone and _db classes and inlined static versions to use time_zone and TZ_DB. I depated separating the 2 options into different headers and implementations but it would add up to 4 files to download for timezones to work.

I modified validate.cpp for the new setup that can take tzfile or tzrule as a command line parameter and test that timezone. When I tested tzfile and tzrule I got the same output except the version line (tzfile doesn't have a version anywhere that I can find) and tzfile has a Factory timezone.

I haven't tested on Windows so hopefully timezone mapping still works.

I also added a CMakeLists.txt for cmake users and modified the *.fail.cpp files to do static_asserts so that they could be tested with ctest. I could do this as a separate PR or just leave it off if you would prefer to keep it as is. Also on my setup parse.pass.cpp is failing an assert, but I don't think it is related to anything I did.

As for performance, running validate tzfile on my system normally takes ~2 seconds. Running validate tzrule takes ~14 seconds without having to download any files. tzfile requires no dependencies or system calls. If you need more up to date tzfiles than what is provided by OSX you can always run zic.

The previous solution would fail, if /etc/localtime is a symlink to a symlink to the zone details. Using realpath resolves all potential symlinks and returns directly the path of interest.

I tested the code below (latest master branch). With USE_OS_TZDB, on Ubuntu 20,04. It crashes with "Unknown error -1".

using namespace date;
using namespace std::chrono;

printf("Searching TZDB\n");
try {
	auto &tzl = get_tzdb_list();
	auto now = system_clock::now();
	for (auto &curTzdb : tzl) {
		for (auto &curTz : curTzdb.zones) {
			auto name = curTz.name();
			if (string::npos != name.find("New_York")) {
				auto curInfo = curTz.get_info(now);
				printf("%s %d %d\n", name.c_str(), (int)curInfo.offset.count(), (int)curInfo.save.count());
			}
		}
	}
} catch (const std::system_error &e) {
	printf("%s\n", e.what());
}

Hi,

First problem:

• Can i use this library in mobile?

Second problem: I have a problem that in our library that work with date and time: https://github.com/ezored/dependency-datetime/blob/master/build/source/cpp/ezored/time/DateTime.cpp#L8

We receive datetime as string, but already in UTC. But when i use on the above method i got time in my current time zone, instead of a chrono object in UTC.

Example:

#include <iostream>
#include <string>
#include <chrono>
#include <sstream>
#include <iomanip>
#include <cstdint>
#include <ctime>

int main()
{
    std::tm tm = {};
    std::stringstream ss("2018-12-07 20:00:00");
    ss >> std::get_time(&tm, "%Y-%m-%d %H:%M:%S");
    auto dt = std::chrono::system_clock::from_time_t(std::mktime(&tm));

    std::cout << (dt.time_since_epoch().count() / 1000000) << std::endl;
    
    // 1544212800 - 20:00 - correct (in utc)
    // 1544223600 - 11:00 - wrong (returned by count)

    return EXIT_SUCCESS;
}

I don't know how to solve it with pure c/c++.

Third problem: How can i solve my problem above using this current library? It it works well i will convert all methods in my library to use this library.

https://github.com/ezored/dependency-datetime/blob/master/build/source/cpp/ezored/time/DateTime.cpp

Im searching for a solution a lot of time, but without solution now.

Merged get_units code for C++11 and C++14, now string_literal are used for all non-custom ratio suffix, that are at most 2 characters [except: decaseconds, minutes, microseconds in char].

This requires to special cases for string_literal, for C++11 mode:

1. Constructor for from string or length 2 (3 elements array)
2. Adding two string literals with size 1.

PR for issue #88 created. As the additions to address the

it will still have to create ostringstream internally for %z and for %S and %T

are non-trivial (they are supported mainly in the subsecs.h file), it will take a bit to get through all the changes in the next comment)

When running testit from release 3.0.1 with OPTIONS='-DONLY_C_LOCALE=1 -DUSE_OS_TZDB=1', the tests posix/ptz.pass.cpp, solar_hijri_test/parse.pass.cpp, and tz_test/zoned_time.pass.cpp fail with error terminate called after throwing an instance of 'std::system_error' - what(): Unknown error -1. When testing the latest master, two tests from tz_test/zoned_time.pass.cpp fail.

This happens when using GCC 10.3.0 on Debian Testing and GCC 11.2.0 on Debian Unstable, but not with Clang 11.1.0 on Debian Testing.

Tested with 3.0.1 with https://github.com/HowardHinnant/date/commit/052eebaf0086e6bbc5ead01c3f1a8f02496aa701 applied and with latest master.

Presumably this is an issue with MacOS 10.13, as it worked on 10.12 last week.

I can compile my code here:

https://github.com/acgetchell/CDT-plusplus

Your date time library is a subrepo in src/date:

https://github.com/acgetchell/CDT-plusplus/tree/master/src/date

Running the compiled code generates the following error:

libc++abi.dylib: terminating with uncaught exception of type std::runtime_error: default/America/Los_Angeles not found in timezone database
Abort trap: 6

I have tried to compile latest version of tz.cpp in my project (gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.4) with -DUSE_OS_TZDB and I get the following error:

FAILED: /usr/bin/c++ -DUSE_OS_TZDB -I../. -I../../ibpp-2.5/core -I../../date -I/home/sur/Projects/boost_1_64_0 -std=c++14 -Wall -Wextra -g -MMD -MT CMakeFiles/crmintegration.dir/home/sur/Projects/date/tz.cpp.o -MF CMakeFiles/crmintegration.dir/home/sur/Projects/date/tz.cpp.o.d -o CMakeFiles/crmintegration.dir/home/sur/Projects/date/tz.cpp.o -c /home/sur/Projects/date/tz.cpp

In file included from /home/sur/Projects/date/tz.cpp:86:0: /home/sur/Projects/date/tz_private.h: In function ‘std::ostream& date::detail::operator<<(std::ostream&, const date::detail::transition&)’: /home/sur/Projects/date/tz_private.h:294:12: error: no match for ‘operator<<’ (operand types are ‘std::ostream {aka std::basic_ostream}’ and ‘const sys_seconds {aka const std::chrono::time_point<std::chrono::_V2::system_clock, std::chrono::duration >}’) os << t.timepoint << "Z "; ^

Help me, please ! :)

Hi Howard, I have finally managed to fix build of the library with Visual Stdio 2013 Update Pack 5. Please review and merge my changes into the mainstream version.

This patch updates the html documentation to add the color-scheme meta element, signalling light and dark color scheme support, and updating the inline CSS styles to override some colors when dark mode is active, to make sure that the document is always readable.

I've also cleaned up a bit the CSS styles, but without functional changes.

I've only updated the latest standard revision (r7), but please let me know if I should revert changes to that file.

Here's how it looks on my system; the dark scheme is provided by the browser:

PS: to be clear, the page is rendered in dark mode only if the user has set dark mode in the browser/system settings

Hi! There is a string format: "2018-12-15 04:49:00+07" How do I get the time_t format? How do I get utc time?

What if the format is like this: "2018-12-15 04:49:00.000+07" How can I get msec separately? Thanks!

If the library gets compiled with HAS_STRING_VIEW=1, consumers always need to link to the functions using std::string_view, as they are the only ones compiled into the shared library.

If the library gets compiled with e.g. C++17 and the user uses an older standard version they'll still get an error, but an helpful compile-time one suggesting to enable C++17 mode, instead of a cryptic linking error.

You can find a longer explanation here: https://github.com/HowardHinnant/date/pull/754#issuecomment-1361248007

   I have one time string : `2022-12-13 10:32:06` . 
   I know  , the time string express the time of `Asia/Shanghai` timezone . 

   How to convert the time string to utc0 time date string : `2022-12-13 02:32:06` ?


   I know de-format date by `date::parse`
   I know format date by `date::format`

   how to convert timestamp(without timezone info) from one timezone to antoher timezone?

Quick question:

Might you tell me the reasoning behind day and month types being cast to unsigned, while year types are cast to int?

Thanks in advance.