Updated Examples and Recipes (markdown)

Howard Hinnant
2016-07-05 23:18:41 -04:00
parent 00e71dd650
commit 5c6ca9fd9e

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This page contains examples and recipes contributed by community members. Feel free to add your own contributions by clicking on the "Edit" button. Please "sign" your contributions by adding a link to your GitHub profile. **But please understand that your contributions will henceforth be considered donated under the [Creative Commons Attribution 4.0 International License](http://creativecommons.org/licenses/by/4.0/)**. If this requirement is a problem for anyone, bring it to Howard's attention and we will try to work out a compromise. This page contains examples and recipes contributed by community members. Feel free to add your own contributions by clicking on the "Edit" button. Please "sign" your contributions by adding a link to your GitHub profile. **But please understand that your contributions will henceforth be considered donated under the [Creative Commons Attribution 4.0 International License](http://creativecommons.org/licenses/by/4.0/)**. If this requirement is a problem for anyone, bring it to Howard's attention and we will try to work out a compromise.
##Contents ##Contents
- [The current local time](#localtime)
- [The current time somewhere else](#elsetime)
- [Obtaining a `time_point` from `y/m/d h:m:s` components](#time_point_to_components) - [Obtaining a `time_point` from `y/m/d h:m:s` components](#time_point_to_components)
- [Obtaining `y/m/d h:m:s` components from a `time_point`](#components_to_time_point) - [Obtaining `y/m/d h:m:s` components from a `time_point`](#components_to_time_point)
- [Normalizing `y/m/d` when it is `!ok()`](#normalize) - [Normalizing `y/m/d` when it is `!ok()`](#normalize)
@@ -19,6 +21,56 @@ This page contains examples and recipes contributed by community members. Feel f
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<a name="localtime"></a>
### The current local time
(by [Howard Hinnant](https://github.com/HowardHinnant))
This couldn't be easier:
```c++
#include "tz.h"
#include <iostream>
int
main()
{
std::cout << date::make_zoned(date::current_zone(), std::chrono::system_clock::now()) << '\n';
}
```
`system_clock::now()` of course gets the current time. It is a de facto standard that this current time is measured in terms of [Unix Time](https://en.wikipedia.org/wiki/Unix_time) which is a very close approximation to UTC. `make_zoned` pairs the current UTC time with the computer's current local time zone, producing a `zoned_time`. The `zoned_time` has a streaming operator so you can easily print it out:
```c++
2016-07-05 23:01:05.818378 EDT
```
Note that the precision of this output is with whatever precision your `system_clock::now()` supports (microseconds on macOS where I'm writing this).
<a name="elsetime"></a>
### The current time somewhere else
(by [Howard Hinnant](https://github.com/HowardHinnant))
If you need to find out the current time where you _aren't_, then that is a simple matter too:
```c++
#include "tz.h"
#include <iostream>
int
main()
{
std::cout << date::make_zoned("Asia/Shanghai", std::chrono::system_clock::now()) << '\n';
}
```
This outputs the current time in Shanghai, for example:
```c++
2016-07-06 11:01:05.818378 CST
```
All IANA timezone names (or links -- aliases to timezones) are supported.
<a name="time_point_to_components"></a> <a name="time_point_to_components"></a>
### Obtaining a `time_point` from `y/m/d h:m:s` components ### Obtaining a `time_point` from `y/m/d h:m:s` components
(by [ecorm](https://github.com/ecorm)) (by [ecorm](https://github.com/ecorm))