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# when [](https://godoc.org/github.com/olebedev/when)
> `when` is a natural language date/time parser with pluggable rules and merge strategies
### Examples
- **tonight at 11:10 pm**
- at **Friday afternoon**
- the deadline is **next tuesday 14:00**
- drop me a line **next wednesday at 2:25 p.m**
- it could be done at **11 am past tuesday**
Check [EN](https://github.com/olebedev/when/blob/master/rules/en) rules and tests of them, for more examples.
**Needed rule not found?**
Open [an issue](https://github.com/olebedev/when/issues/new) with the case and it will be added asap.
### How it works
Usually, there are several rules added to the parser's instance for checking. Each rule has its own borders - length and offset in provided string. Meanwhile, each rule yields only the first match over the string. So, the library checks all the rules and extracts a cluster of matched rules which have distance between each other less or equal to [`options.Distance`](https://github.com/olebedev/when/blob/master/when.go#L141-L144), which is 5 by default. For example:
```
on next wednesday at 2:25 p.m.
└──────┬─────┘ └───┬───┘
weekday hour + minute
```
So, we have a cluster of matched rules - `"next wednesday at 2:25 p.m."` in the string representation.
After that, each rule is applied to the context. In order of definition or in match order, if [`options.MatchByOrder`](https://github.com/olebedev/when/blob/master/when.go#L141-L144) is set to `true`(which it is by default). Each rule could be applied with given merge strategy. By default, it's an [Override](https://github.com/olebedev/when/blob/master/rules/rules.go#L13) strategy. The other strategies are not implemented yet in the rules. **Pull requests are welcome.**
### Supported Languages
- [EN](https://github.com/olebedev/when/blob/master/rules/en) - English
- [RU](https://github.com/olebedev/when/blob/master/rules/ru) - Russian
- [BR](https://github.com/olebedev/when/blob/master/rules/br) - Brazilian Portuguese
- [ZH](https://github.com/olebedev/when/blob/master/rules/zh) - Chinese
- [NL](https://github.com/olebedev/when/blob/master/rules/nl) - Dutch
### Install
The project follows the official [release workflow](https://go.dev/doc/modules/release-workflow). It is recommended to refer to this resource for detailed information on the process.
To install the latest version:
```
$ go get github.com/olebedev/when@latest
```
### Usage
```go
w := when.New(nil)
w.Add(en.All...)
w.Add(common.All...)
text := "drop me a line in next wednesday at 2:25 p.m"
r, err := w.Parse(text, time.Now())
if err != nil {
// an error has occurred
}
if r == nil {
// no matches found
}
fmt.Println(
"the time",
r.Time.String(),
"mentioned in",
text[r.Index:r.Index+len(r.Text)],
)
```
#### Distance Option
```go
w := when.New(nil)
w.Add(en.All...)
w.Add(common.All...)
text := "February 23, 2019 | 1:46pm"
// With default distance (5):
// February 23, 2019 | 1:46pm
// └───┬───┘
// distance: 9 (1:46pm will be ignored)
r, _ := w.Parse(text, time.Now())
fmt.Printf(r.Time.String())
// "2019-02-23 09:21:21.835182427 -0300 -03"
// 2019-02-23 (correct)
// 09:21:21 ("wrong")
// With custom distance (10):
w.SetOptions(&rules.Options{
Distance: 10,
MatchByOrder: true})
r, _ = w.Parse(text, time.Now())
fmt.Printf(r.Time.String())
// "2019-02-23 13:46:21.559521554 -0300 -03"
// 2019-02-23 (correct)
// 13:46:21 (correct)
```
### State of the project
The project is in a more-or-less complete state. It's used for one project already. Bugs will be fixed as soon as they will be found.
### TODO
- [ ] readme: describe all the existing rules
- [ ] implement missed rules for [these examples](https://github.com/mojombo/chronic#examples)
- [ ] add cli and simple rest api server([#2](https://github.com/olebedev/when/issues/2))
### LICENSE
http://www.apache.org/licenses/LICENSE-2.0
|
