gtz

A timezone data provider for Gleam!

gleam add gtz
# Choose which package to use for other time functionality
gleam add gtempo
gleam add gleam_time

This package has functions to be used with the gtempo package and the gleam_time package. Currently this package is very simple: it only supports converting non-naive datetimes to a specific timezone via gtempo, and calculating an offset given a timestamp and time zone via the gleam_time types. Contributions are welcome!

Supports both the Erlang and JavaScript targets. On Erlang the timezone data comes from the operating system’s TZif files (typically /usr/share/zoneinfo) via the tzif package, loaded once and cached in a persistent term; on JavaScript it comes from the native Intl API.

Calculating Offsets In a Time Zone

import gleam/time/timestamp
import gtz

let my_ts = timestamp.from_unix_seconds(1_729_257_776)

let assert Ok(ny_offset) = 
  gtz.calculate_offset(my_ts, in: "America/New_York")

// Now that we have the offset for the timestamp in the desired time zone, we 
// can convert it to a calendar date and time
timestamp.to_calendar(my_ts, ny_offset)
// -> #(
//   calendar.Date(2024, calendar.October, 18),
//   calendar.TimeOfDay(9, 22, 56, 0)
// )

Converting DateTimes to the Local Timezone

import gtz
import tempo/datetime

pub fn main() {
  let assert Ok(local_tz) = gtz.local_name() |> gtz.timezone

  datetime.from_unix_utc(1_729_257_776)
  |> datetime.to_timezone(local_tz)
  |> datetime.to_string
}
// -> "2024-10-18T14:22:56.000+01:00"

Converting DateTimes to a Specific Timezone

import gtz
import tempo/datetime

pub fn main() {
  let assert Ok(tz) = gtz.timezone("America/New_York")

  datetime.literal("2024-01-03T05:30:02.334Z")
  |> datetime.to_timezone(tz)
  |> datetime.to_string
}
// -> "2024-01-03T00:30:02.334-05:00"

Further documentation can be found at https://hexdocs.pm/gtz.

Development

gleam run   # Run the project
gleam test  # Run the tests