# erlang_localtime

**Repository Path**: summergaolib/erlang_localtime

## Basic Information

- **Project Name**: erlang_localtime
- **Description**: Erlang library for conversion from one local time to another
- **Primary Language**: Unknown
- **License**: Apache-2.0
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2020-06-09
- **Last Updated**: 2020-12-19

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README


Erlang Localtime
===


### Public exports

* `utc_to_local/2` – Converts UTC time to local according to specified Timezone
* `local_to_utc/2` – Converts local time to UTC
* `local_to_local/3` – Converts local time to local
* `tz_name/2` – Returns a timezone name (E.g. MSK, MSD, etc)
* `tz_shift/2` – Returns time difference between local datetime and GMT
* `tz_shift/3` – Returns time difference between local datetime and required timezone

### Details

#### Types
* `DateTime` = `{date(), time()}`.
* `TimeZone` = `TimeZoneFrom` = `TimeZoneTo` = `list()`, e.g. `"Europe/Moscow"`, `"America/NewYork"` or abbreviations `"MSK"`, `"MSD"`, etc.
* `ZoneName` =  `{StdAbbr :: list(), StdName :: list()}`, e.g. `{"MSK","MSK"}`
* `ZoneShift` = `{Sign :: '+' | '-', Offset :: non_neg_integer(), RemOffset :: non_neg_integer()}`

#### Dialyzer

`utc_to_local(DateTime, TimeZone) → DateTime | {error, Reason}`

`local_to_utc(DateTime, TimeZone) → DateTime | {error, Reason}`

`local_to_local(DateTime, TimeZoneFrom, TimeZoneTo) → DateTime | {error, Reason}`

`tz_name(DateTime, TimeZone) → ZoneName | {error, Reason}`

`tz_shift(DateTime, TimeZone) → 0 | ZoneShift | {error, Reason}`

`tz_shift(DateTime, TimeZoneFrom, TimeZoneTo) → 0 | ZoneShift | {error, Reason}`

#### Note

Aabbreviation is just used to find appropriate timezone name. If you want to convert `"MSK"` → `"PDT"`, but source timezone is not in daylight saving, it will be corrected by library and `"MSK"` → `"PST"` conversion will be made.

### Examples of usage

#### Converts UTC time to local one
```erlang
localtime:utc_to_local({{2010, 7, 22}, {17, 56, 23}}, "Europe/Moscow").
{{2010,10,10},{21,56,23}}
```

#### Converts local time to UTC one
```erlang
localtime:local_to_utc({{2010, 10, 10}, {21, 56, 23}}, "Europe/Moscow").
{{2010,10,10},{17,56,23}}
```

#### Converts time from one local timezone to another local one
```erlang
localtime:local_to_local({{2010, 10, 10}, {21, 56, 23}}, "Europe/Moscow", "Australia/Sydney").
{{2010,10,11},{3,56,23}}
```

#### Returns timezone name
```erlang
localtime:tz_name({{2010, 10, 10}, {21, 56, 23}}, "Europe/Moscow").
{"MSK","MSK"}

localtime:tz_name({{2010,10,11},{3,56,23}}, "Australia/Sydney").
{"EST","EST"}
```

#### Calculates time difference between UTC and local one
```erlang
localtime:tz_shift({{2013, 01, 22}, {18, 17, 00}}, "Europe/Moscow").
{'+',4,0}

localtime:tz_shift({{2013, 01, 22}, {18, 17, 00}}, "America/New York").
{'-',5,0}
```

#### Calculates time difference between two local timezones
```erlang
localtime:tz_shift({{2013, 01, 22}, {18, 17, 00}}, "America/New York", "Europe/Moscow").
{'+',9,0}
```