defmodule Timex.Timezone do
@moduledoc """
This module is used for looking up the timezone information for
a given point in time, in the desired zone. Timezones are dependent
not only on locale, but the date and time for which you are querying.
For instance, the timezone offset from UTC for `Europe/Moscow` is different
for March 3rd of 2015, than it was in 2013. These differences are important,
and as such, all functions in this module are date/time sensitive, and where
omitted, the current date/time are assumed.
In addition to lookups, this module also does conversion of datetimes from one
timezone period to another, and determining the difference between a date in one
timezone period and the same date/time in another timezone period.
"""
alias Timex.AmbiguousDateTime
alias Timex.TimezoneInfo
alias Timex.PosixTimezone
alias Timex.AmbiguousTimezoneInfo
alias Timex.Timezone.Local, as: Local
alias Timex.Parse.Timezones.Posix
alias Timex.Types
@doc """
Determines if a given zone name exists
"""
@spec exists?(String.t()) :: boolean
def exists?(zone) when is_binary(zone) do
if Tzdata.zone_exists?(zone) do
true
else
case lookup_posix(zone) do
%PosixTimezone{} -> true
_ -> false
end
end
end
@doc """
Gets the local timezone configuration for the current date and time.
"""
@spec local() :: TimezoneInfo.t() | AmbiguousTimezoneInfo.t() | {:error, term}
def local(), do: local(:calendar.universal_time())
@doc """
Gets the local timezone configuration for the provided date and time.
The provided date and time can either be an Erlang datetime tuple, or a DateTime struct.
"""
@spec local(Types.valid_datetime()) ::
TimezoneInfo.t() | AmbiguousTimezoneInfo.t() | {:error, term}
def local(date) do
secs = Timex.to_gregorian_seconds(date)
case Local.lookup() do
{:error, _} = err ->
err
tz ->
resolve(tz, secs)
end
end
@doc """
This function takes one of the varying timezone representations:
- atoms
- offset integers
- shortcut names (i.e. :utc, :local, "Z", "A")
and resolves the full name of the timezone if it's able.
If a string is provided which isn't recognized, it is returned untouched,
only when `get/2` is called will the timezone lookup fail.
"""
@spec name_of(Types.valid_timezone() | TimezoneInfo.t() | AmbiguousTimezoneInfo.t()) ::
String.t()
| {:error, :time_zone_not_found}
| {:error, term}
def name_of(%TimezoneInfo{:full_name => name}), do: name
def name_of(:utc), do: "Etc/UTC"
def name_of(:local), do: name_of(Local.lookup())
def name_of("Etc/UTC"), do: "Etc/UTC"
def name_of("GMT"), do: "Etc/UTC"
def name_of("UTC"), do: "Etc/UTC"
def name_of("UT"), do: "Etc/UTC"
def name_of("Z"), do: "Etc/UTC"
def name_of("A"), do: "Etc/UTC+1"
def name_of("M"), do: "Etc/UTC+12"
def name_of("N"), do: "Etc/UTC-1"
def name_of("Y"), do: "Etc/UTC-12"
def name_of(0), do: "Etc/UTC"
def name_of(offset) when is_integer(offset) do
cond do
offset <= -100 ->
hh = div(offset * -1, 100)
mm = rem(offset, 100) * -1
if mm == 0 do
"Etc/UTC-#{hh}"
else
hh = String.pad_leading(to_string(hh), 2, "0")
mm = String.pad_leading(to_string(mm), 2, "0")
"Etc/UTC-#{hh}:#{mm}"
end
offset >= 100 ->
hh = div(offset, 100)
mm = rem(offset, 100)
if mm == 0 do
"Etc/UTC+#{hh}"
else
hh = String.pad_leading(to_string(hh), 2, "0")
mm = String.pad_leading(to_string(mm), 2, "0")
"Etc/UTC+#{hh}:#{mm}"
end
offset >= 0 and offset < 24 ->
"Etc/UTC+#{offset}"
offset <= 0 and offset > -24 ->
"Etc/UTC-#{offset * -1}"
:else ->
{:error, :time_zone_not_found}
end
end
def name_of(<<sign::utf8, ?0, ?0, ?:, ?0, ?0>>) when sign in [?+, ?-] do
"Etc/UTC"
end
def name_of(<<sign::utf8, h::binary-size(2)-unit(8), ?:, ?0, ?0>>) when sign in [?+, ?-] do
"Etc/UTC" <> <<sign::utf8, h::binary>>
end
def name_of(<<sign::utf8, h::binary-size(1)-unit(8), ?:, ?0, ?0>>) when sign in [?+, ?-] do
"Etc/UTC" <> <<sign::utf8, h::binary>>
end
def name_of(<<sign::utf8, h::binary-size(2)-unit(8), ?:, m::binary-size(2)-unit(8)>>)
when sign in [?+, ?-] do
"Etc/UTC" <> <<sign::utf8, h::binary, ?:, m::binary>>
end
def name_of(<<sign::utf8, h::binary-size(1)-unit(8), ?:, m::binary-size(2)-unit(8)>>)
when sign in [?+, ?-] do
"Etc/UTC" <> <<sign::utf8, h::binary, ?:, m::binary>>
end
def name_of(
<<sign::utf8, h::binary-size(2)-unit(8), ?:, m::binary-size(2)-unit(8), ?:,
s::binary-size(2)-unit(8)>>
)
when sign in [?+, ?-] do
"Etc/UTC" <> <<sign::utf8, h::binary, ?:, m::binary, ?:, s::binary>>
end
def name_of(
<<sign::utf8, h::binary-size(1)-unit(8), ?:, m::binary-size(2)-unit(8), ?:,
s::binary-size(2)-unit(8)>>
)
when sign in [?+, ?-] do
"Etc/UTC" <> <<sign::utf8, h::binary, ?:, m::binary, ?:, s::binary>>
end
def name_of(<<sign::utf8, h::binary-size(2)-unit(8), m::binary-size(2)-unit(8)>>)
when sign in [?+, ?-] do
"Etc/UTC" <> <<sign::utf8, h::binary, ?:, m::binary>>
end
def name_of(<<sign::utf8, h::binary-size(1)-unit(8), m::binary-size(2)-unit(8)>>)
when sign in [?+, ?-] do
"Etc/UTC" <> <<sign::utf8, h::binary, ?:, m::binary>>
end
def name_of(<<sign::utf8, h::binary-size(2)-unit(8)>>) when sign in [?+, ?-] do
"Etc/UTC" <> <<sign::utf8, h::binary>>
end
def name_of(<<sign::utf8, h::utf8>>) when sign in [?+, ?-] and h >= ?0 and h <= ?9 do
"Etc/UTC" <> <<sign::utf8, h::utf8>>
end
def name_of("Etc/UTC" <> offset), do: name_of(offset)
def name_of("Etc/GMT" <> offset) do
case name_of("GMT" <> offset) do
{:error, _} = err ->
err
<<"Etc/UTC", ?+, rest::binary>> ->
"Etc/GMT-" <> rest
<<"Etc/UTC", ?-, rest::binary>> ->
"Etc/GMT+" <> rest
other ->
other
end
end
def name_of(<<"GMT", sign::utf8, hh::utf8>>) when sign in [?+, ?-],
do: "Etc/UTC" <> <<sign::utf8, hh::utf8>>
def name_of(<<"GMT", sign::utf8, hh::binary-size(2)-unit(8)>>) when sign in [?+, ?-],
do: "Etc/UTC" <> <<sign::utf8, hh::binary>>
def name_of(<<"GMT", sign::utf8, hh::binary-size(2)-unit(8), ?:, mm::binary-size(2)-unit(8)>>)
when sign in [?+, ?-],
do: "Etc/UTC" <> <<sign::utf8, hh::binary, ?:, mm::binary>>
def name_of(<<"GMT", sign::utf8, hh::binary-size(1)-unit(8), ?:, mm::binary-size(2)-unit(8)>>)
when sign in [?+, ?-],
do: "Etc/UTC" <> <<sign::utf8, hh::binary, ?:, mm::binary>>
def name_of(<<"GMT", sign::utf8, hh::binary-size(2)-unit(8), mm::binary-size(2)-unit(8)>>)
when sign in [?+, ?-],
do: "Etc/UTC" <> <<sign::utf8, hh::binary, ?:, mm::binary>>
def name_of(<<"GMT", sign::utf8, hh::binary-size(1)-unit(8), mm::binary-size(2)-unit(8)>>)
when sign in [?+, ?-],
do: "Etc/UTC" <> <<sign::utf8, hh::binary, ?:, mm::binary>>
def name_of(""), do: {:error, :time_zone_not_found}
def name_of(tz) when is_binary(tz) do
if Tzdata.zone_exists?(tz) do
tz
else
case lookup_posix(tz) do
%PosixTimezone{name: name} ->
name
nil ->
{:error, :time_zone_not_found}
end
end
end
def name_of(_tz), do: {:error, :time_zone_not_found}
@doc """
Gets timezone info for a given zone name and date. The date provided
can either be an Erlang datetime tuple, or a DateTime struct, and if one
is not provided, then the current date and time is returned.
"""
@spec get(Types.valid_timezone()) ::
TimezoneInfo.t() | AmbiguousTimezoneInfo.t() | {:error, term}
@spec get(Types.valid_timezone(), Types.valid_datetime()) ::
TimezoneInfo.t() | AmbiguousTimezoneInfo.t() | {:error, term}
def get(tz, datetime \\ NaiveDateTime.utc_now())
def get(:utc, _datetime), do: %TimezoneInfo{}
def get(:local, datetime), do: local(datetime)
def get(tz, datetime) do
utc_or_wall = if match?(%DateTime{}, datetime), do: :utc, else: :wall
case name_of(tz) do
{:error, _} = err ->
err
name ->
get_info(name, datetime, utc_or_wall)
end
end
@doc """
Same as `get/2`, but allows specifying whether to obtain the TimezoneInfo based
on utc time or wall time manually (`:utc` or `:wall` respectively).
"""
def get(:utc, _, _), do: %TimezoneInfo{}
def get(:local, datetime, _), do: local(datetime)
def get(tz, datetime, utc_or_wall) do
case name_of(tz) do
{:error, _} = err ->
err
name ->
get_info(name, datetime, utc_or_wall)
end
end
defp get_info(timezone, datetime, utc_or_wall)
defp get_info("Etc/UTC", _datetime, _utc_or_wall),
do: %TimezoneInfo{}
defp get_info("Etc/GMT", _datetime, _utc_or_wall),
do: %TimezoneInfo{}
defp get_info(<<"Etc/UTC", sign::utf8, offset::binary>>, datetime, utc_or_wall)
when sign in [?+, ?-] do
get_utc_info("Etc/UTC", <<sign::utf8, offset::binary>>, datetime, utc_or_wall)
end
defp get_info(<<"Etc/GMT", sign::utf8, offset::binary>>, datetime, utc_or_wall)
when sign in [?+, ?-] do
get_utc_info("Etc/GMT", <<sign::utf8, offset::binary>>, datetime, utc_or_wall)
end
defp get_info(<<"GMT", sign::utf8, offset::binary>>, _datetime, _utc_or_wall)
when sign in [?+, ?-] do
with offset_secs when is_integer(offset_secs) <- parse_offset(offset) do
hours = div(offset_secs, 3600)
minutes = div(rem(offset_secs, 3600), 60)
if hours != 0 or minutes != 0 do
hh = String.pad_leading(to_string(hours), 2, "0")
mm = String.pad_leading(to_string(minutes), 2, "0")
{suffix, abbr, offset_utc} =
cond do
sign == ?+ and minutes == 0 ->
{"+#{hours}", "-#{hh}", offset_secs * -1}
sign == ?+ ->
{"+#{hours}:#{mm}", "-#{hh}:#{mm}", offset_secs * -1}
sign == ?- and minutes == 0 ->
{"-#{hours}", "+#{hh}", offset_secs}
sign == ?- ->
{"-#{hours}:#{mm}", "+#{hh}:#{mm}", offset_secs}
end
%TimezoneInfo{
full_name: <<"Etc/GMT", suffix::binary>>,
abbreviation: abbr,
offset_std: 0,
offset_utc: offset_utc,
from: :min,
until: :max
}
else
%TimezoneInfo{
full_name: "Etc/GMT",
abbreviation: "GMT",
offset_std: 0,
offset_utc: 0,
from: :min,
until: :max
}
end
end
end
defp get_info(name, datetime, utc_or_wall) when is_binary(name) do
seconds_from_zeroyear = Timex.to_gregorian_seconds(datetime)
if Tzdata.zone_exists?(name) do
resolve(name, seconds_from_zeroyear, utc_or_wall)
else
with {:ok, %PosixTimezone{} = posixtz, _} <- Posix.parse(name) do
PosixTimezone.to_timezone_info(posixtz, Timex.to_naive_datetime(datetime))
else
{:error, _, _} ->
{:error, :time_zone_not_found}
end
end
end
defp get_info(%TimezoneInfo{} = info, _datetime, _utc_or_wall), do: info
defp get_utc_info(prefix, <<sign::utf8, offset::binary>>, _datetime, _utc_or_wall)
when sign in [?+, ?-] do
with offset_secs when is_integer(offset_secs) <- parse_offset(offset) do
hours = div(offset_secs, 3600)
minutes = div(rem(offset_secs, 3600), 60)
if hours != 0 or minutes != 0 do
hh = String.pad_leading(to_string(hours), 2, "0")
mm = String.pad_leading(to_string(minutes), 2, "0")
{suffix, abbr, offset_utc} =
cond do
sign == ?+ and minutes == 0 ->
{"#{hours}", "+#{hh}", offset_secs}
sign == ?+ ->
{"#{hours}:#{mm}", "+#{hh}:#{mm}", offset_secs}
sign == ?- and minutes == 0 ->
{"#{hours}", "-#{hh}", offset_secs * -1}
sign == ?- ->
{"#{hours}:#{mm}", "-#{hh}:#{mm}", offset_secs * -1}
end
%TimezoneInfo{
full_name: <<prefix::binary, sign::utf8, suffix::binary>>,
abbreviation: abbr,
offset_std: 0,
offset_utc: offset_utc,
from: :min,
until: :max
}
else
%TimezoneInfo{}
end
end
end
defp parse_offset(
<<h::binary-size(2)-unit(8), ?:, m::binary-size(2)-unit(8), ?:,
s::binary-size(2)-unit(8)>>
) do
with {hh, _} <- Integer.parse(h),
{mm, _} <- Integer.parse(m),
{ss, _} <- Integer.parse(s) do
hh * 3600 + mm * 60 + ss
else
_ ->
{:error, :invalid_offset}
end
end
defp parse_offset(
<<h::binary-size(1)-unit(8), ?:, m::binary-size(2)-unit(8), ?:,
s::binary-size(2)-unit(8)>>
) do
with {hh, _} <- Integer.parse(h),
{mm, _} <- Integer.parse(m),
{ss, _} <- Integer.parse(s) do
hh * 3600 + mm * 60 + ss
else
_ ->
{:error, :invalid_offset}
end
end
defp parse_offset(<<h::binary-size(2)-unit(8), ?:, m::binary-size(2)-unit(8)>>) do
with {hh, _} <- Integer.parse(h),
{mm, _} <- Integer.parse(m) do
hh * 3600 + mm * 60
else
_ ->
{:error, :invalid_offset}
end
end
defp parse_offset(<<h::binary-size(1)-unit(8), ?:, m::binary-size(2)-unit(8)>>) do
with {hh, _} <- Integer.parse(h),
{mm, _} <- Integer.parse(m) do
hh * 3600 + mm * 60
else
_ ->
{:error, :invalid_offset}
end
end
defp parse_offset(<<h::binary-size(2)-unit(8)>>) do
with {hh, _} <- Integer.parse(h) do
hh * 3600
else
_ ->
{:error, :invalid_offset}
end
end
defp parse_offset(<<h::utf8>> = input) when h >= ?0 and h <= ?9 do
String.to_integer(input) * 3600
end
def total_offset(%TimezoneInfo{offset_std: std, offset_utc: utc}) do
utc + std
end
def total_offset(std_offset, utc_offset)
when is_integer(std_offset) and is_integer(utc_offset) do
utc_offset + std_offset
end
@doc """
Given a timezone name as a string, and a date/time in the form of the number of seconds since year zero,
attempt to resolve a TimezoneInfo for that date/time. If the time is ambiguous, AmbiguousTimezoneInfo will
be returned. If no result is found, an error will be returned.
If an invalid zone name is provided, an error will be returned
"""
@spec resolve(String.t(), non_neg_integer, :utc | :wall) ::
TimezoneInfo.t()
| AmbiguousTimezoneInfo.t()
| {:error, term}
def resolve(tzname, datetime, utc_or_wall \\ :wall)
def resolve(name, seconds_from_zeroyear, utc_or_wall)
when is_binary(name) and is_integer(seconds_from_zeroyear) and utc_or_wall in [:utc, :wall] do
case Tzdata.periods_for_time(name, seconds_from_zeroyear, utc_or_wall) do
[] ->
{:error, {:could_not_resolve_timezone, name, seconds_from_zeroyear, utc_or_wall}}
# Resolved
[period] ->
tzdata_to_timezone(period, name)
# This case happens when using wall clock time, we resolve it by using UTC clock time instead
[before_period, after_period | _] ->
case Tzdata.periods_for_time(name, seconds_from_zeroyear, :utc) do
[] ->
# We can't resolve it this way, I don't expect this to be possible, but we handle it
before_tz = tzdata_to_timezone(before_period, name)
after_tz = tzdata_to_timezone(after_period, name)
AmbiguousTimezoneInfo.new(before_tz, after_tz)
[period] ->
tzdata_to_timezone(period, name)
_ ->
# Still ambiguous, use wall clock time for info passed back to caller
before_tz = tzdata_to_timezone(before_period, name)
after_tz = tzdata_to_timezone(after_period, name)
AmbiguousTimezoneInfo.new(before_tz, after_tz)
end
end
end
@doc """
Convert a date to the given timezone (either TimezoneInfo or a timezone name)
"""
@spec convert(date :: DateTime.t() | NaiveDateTime.t(), tz :: AmbiguousTimezoneInfo.t()) ::
AmbiguousDateTime.t() | {:error, term}
@spec convert(
date :: DateTime.t() | NaiveDateTime.t(),
tz :: TimezoneInfo.t() | Types.valid_timezone()
) ::
DateTime.t() | AmbiguousDateTime.t() | {:error, term}
def convert(%DateTime{} = date, %AmbiguousTimezoneInfo{} = tz) do
before_date = convert(date, tz.before)
after_date = convert(date, tz.after)
%AmbiguousDateTime{:before => before_date, :after => after_date}
end
def convert(%DateTime{time_zone: name} = date, %TimezoneInfo{full_name: name}) do
# Do not convert date when already in destination time zone
date
end
def convert(%DateTime{} = date, %TimezoneInfo{full_name: name}) do
with {:ok, datetime} <- DateTime.shift_zone(date, name, Timex.Timezone.Database) do
datetime
else
{ty, a, b} when ty in [:gap, :ambiguous] ->
%AmbiguousDateTime{before: a, after: b, type: ty}
{:error, _} = err ->
err
end
end
def convert(%DateTime{} = date, tz) do
case get(tz, date) do
{:error, _} = err ->
err
timezone ->
convert(date, timezone)
end
end
def convert(%NaiveDateTime{} = date, %AmbiguousTimezoneInfo{} = tz) do
before_date = convert(date, tz.before)
after_date = convert(date, tz.after)
%AmbiguousDateTime{:before => before_date, :after => after_date}
end
def convert(%NaiveDateTime{} = date, %TimezoneInfo{full_name: name}) do
with {:ok, datetime} <- DateTime.from_naive(date, name, Timex.Timezone.Database) do
datetime
else
{ty, a, b} when ty in [:gap, :ambiguous] ->
%AmbiguousDateTime{before: a, after: b, type: ty}
{:error, _} = err ->
err
end
end
def convert(%NaiveDateTime{} = date, tz) do
with %TimezoneInfo{} = tzinfo <- get(tz, date) do
convert(date, tzinfo)
end
end
def convert(date, tz) do
case Timex.to_datetime(date, tz) do
{:error, _} = err ->
err
datetime ->
datetime
end
end
@doc """
Shifts the provided DateTime to the beginning of the day in it's timezone
"""
@spec beginning_of_day(DateTime.t()) :: DateTime.t()
def beginning_of_day(%DateTime{time_zone: tz, microsecond: {_, precision}} = dt) do
do_beginning_of_day(dt, tz, {{dt.year, dt.month, dt.day}, {0, 0, 0}}, precision)
end
defp do_beginning_of_day(%DateTime{} = dt, tz, {date, {h, _, _}} = day_start, precision) do
abs_start = :calendar.datetime_to_gregorian_seconds(day_start)
case Tzdata.zone_exists?(tz) do
true ->
case Tzdata.periods_for_time(tz, abs_start, :wall) do
# This hour does not exist, so move ahead one and try again
[] ->
do_beginning_of_day(dt, tz, {date, {h + 1, 0, 0}}, precision)
# Only one period applies
[%{utc_off: utc_offset, std_off: std_offset, zone_abbr: abbr}] ->
%{
dt
| :hour => h,
:minute => 0,
:second => 0,
:microsecond => {0, precision},
:utc_offset => utc_offset,
:std_offset => std_offset,
:zone_abbr => abbr
}
# Ambiguous, choose the earliest one in the same day which is unambiguous
[_, _] ->
do_beginning_of_day(dt, tz, {date, {h + 1, 0, 0}}, precision)
end
false ->
%{dt | :hour => 0, :minute => 0, :second => 0, :microsecond => {0, precision}}
end
end
@doc """
Shifts the provided DateTime to the end of the day in it's timezone
"""
@spec end_of_day(DateTime.t()) :: DateTime.t()
def end_of_day(%DateTime{time_zone: tz, microsecond: {_, precision}} = dt) do
do_end_of_day(dt, tz, {{dt.year, dt.month, dt.day}, {23, 59, 59}}, precision)
end
defp do_end_of_day(%DateTime{} = dt, tz, {date, {h, _, _}} = day_end, precision) do
abs_end = :calendar.datetime_to_gregorian_seconds(day_end)
case Tzdata.zone_exists?(tz) do
true ->
case Tzdata.periods_for_time(tz, abs_end, :wall) do
# This hour does not exist, so move back one and try again
[] ->
do_end_of_day(dt, tz, {date, {h - 1, 59, 59}}, precision)
# Only one period applies
[%{utc_off: utc_offset, std_off: std_offset, zone_abbr: abbr}] ->
%{
dt
| :hour => h,
:minute => 59,
:second => 59,
:microsecond => Timex.DateTime.Helpers.construct_microseconds(999_999, precision),
:utc_offset => utc_offset,
:std_offset => std_offset,
:zone_abbr => abbr
}
# Ambiguous, choose the earliest one in the same day which is unambiguous
[_, _] ->
do_beginning_of_day(dt, tz, {date, {h - 1, 59, 59}}, precision)
end
false ->
us = Timex.DateTime.Helpers.construct_microseconds(999_999, precision)
%{dt | :hour => 23, :minute => 59, :second => 59, :microsecond => us}
end
end
@spec tzdata_to_timezone(map, String.t()) :: TimezoneInfo.t()
def tzdata_to_timezone(
%{
from: %{wall: from},
std_off: std_off_secs,
until: %{wall: until},
utc_off: utc_off_secs,
zone_abbr: abbr
} = _tzdata,
zone
) do
start_bound = boundary_to_erlang_datetime(from)
end_bound = boundary_to_erlang_datetime(until)
%TimezoneInfo{
full_name: zone,
abbreviation: abbr,
offset_std: std_off_secs,
offset_utc: utc_off_secs,
from: erlang_datetime_to_boundary_date(start_bound),
until: erlang_datetime_to_boundary_date(end_bound)
}
end
@spec boundary_to_erlang_datetime(:min | :max | integer) :: :min | :max | Types.datetime()
defp boundary_to_erlang_datetime(:min), do: :min
defp boundary_to_erlang_datetime(:max), do: :max
defp boundary_to_erlang_datetime(secs), do: :calendar.gregorian_seconds_to_datetime(trunc(secs))
@spec erlang_datetime_to_boundary_date(:min | :max | Types.datetime()) ::
:min | :max | {Types.weekday_name()}
defp erlang_datetime_to_boundary_date(:min), do: :min
defp erlang_datetime_to_boundary_date(:max), do: :max
defp erlang_datetime_to_boundary_date({{y, m, d}, _} = date) do
dow =
case :calendar.day_of_the_week({y, m, d}) do
1 -> :monday
2 -> :tuesday
3 -> :wednesday
4 -> :thursday
5 -> :friday
6 -> :saturday
7 -> :sunday
end
{dow, date}
end
@doc false
@spec lookup_posix(String.t()) :: PosixTimezone.t() | nil
def lookup_posix(timezone) when is_binary(timezone) do
with {:ok, %PosixTimezone{} = posixtz, _} <- Posix.parse(timezone) do
posixtz
else
_ ->
nil
end
end
def lookup_posix(_), do: nil
end
