@tubular/time-tzdb

@tubular/time-tzdb is an IANA timezone compiler, specifically for generating timezone data compatible with @tubular/time, but also capable of generating standard zoneinfo/zic-style binaries.

It can compile timezone source files directly from , using the latest release or any particular requested version, or from a local .tar.gz file specified via file URL.

Options are available for limiting the span of years covered, adjusting and filtering timezones, and choosing different output formats.

- @tubular/time-tzdb
- Requirements
- Installation
- As a command line tool
- As a library
- CLI interface
- JavaScript/TypeScript API
- getTzData
- writeTimezones
- Listing available tz database releases
- @tubular/time data format
- Timezone descriptions
- Base-60 numbers
- Not-entirely-formal Extended BNF for timezone description syntax
- Simple timezone alias
- Pseudo-alias
- Modified pseudo-alias

Requirements

Your system should have a command line awk tool installed for full functionality. Without it, the “vanguard” and “rearguard” options are not fully supported.

Installation

$3

npm install -g @tubular/time-tzdb

$3

npm install @tubular/time-tzdb

const { getAvailableVersions, getTzData, writeTimezones...} = require('@tubular/time_tzdb');

import { getAvailableVersions, getTzData, writeTimezones...} from '@tubular/time_tzdb';

CLI interface

``text Usage: tzc [options] [output_file_name_or_directory]

Downloads and compiles IANA timezone data, converting to text, zoneinfo binary files, or @tubular/time-compatible data.

Options: -v, --version output the version number -5, --systemv Include the SystemV timezones from the systemv file by uncommenting the commented-out zone descriptions. -b, --binary Output binary files to a directory, one file per timezone -B, --bloat Equivalent to the zic "--bloat fat" option. -f Filter out Etc/GMTxxx and other timezones that are either redundant or covered by options for creating fixed-offset timezones. -i Include leap seconds in binary files. -j, --javascript Output JavaScript instead of JSON. --large Apply presets for "large" timezone definitions. --large-alt Apply presets for "large-alt" timezone definitions. --list List available tz database versions. -m Round all UTC offsets to whole minutes. -n, --no-backward Skip the additional aliases in the backward file. -o Overwrite existing file/directory. -q Display no progress messages, fewer warning messages. -R, --rearguard Rearguard mode (skip vanguard features like negative DST). -r Remove 'calendar rollbacks' from time zone transitions -- that is modify time zone data to prevent situations where the calendar date goes backwards as well as the hour and/or minute of the day. -p, --packrat Add additional timezones from the backzone file. -s ID/name for a single timezone/region to be rendered. --small Apply presets for "small" timezone definitions. -t, --typescript Output TypeScript instead of JSON. --text Output (somewhat) human-readable text -u, --url URL or version number, such as '2018c', to parse and compile. Default: https://www.iana.org/time-zones/repository/tzdata-latest.tar.gz -V, --vanguard Vanguard mode (use vanguard features like negative DST). -y Year range for explicit time zone transitions. Default: 1850,2050 -z Validate this tool's output against output from the standard zic tool stored in the given directory. (Validation is done before applying the -r option.) -h, --help display help for command -, Use dash by itself to output to stdout.`

The default output filename, if not specified, is timezones._ext_, where _ext_ is one of json, js, ts, or txt depending on the selected output format.

If you specify your own output filename using one of the extensions json, js, ts, or txt a matching format will automatically be selected. If you specify no extension, an appropriate extension will be appended.

If you use any of the options --small, --large, or --large-alt, the default root of the output filename for text formats becomes timezone-small, timezone-large, or timezone-large-alt respectively.

For binary output, the default directory is zoneinfo in the current working directory. The - option for output to stdout does not apply to binary files.

Please read the API description for a more complete understanding of all the CLI options.

`JavaScript/TypeScript API`

`$3`

async function getTzData(options: TzOptions = {}): Promise

This function returns an object (or string — only TzFormat.JSON format can be returned as an object) containing encoded timezone information for a set of timezones, and other timezone set metadata. This data is in a format meant to be consumed by the @tubular/time package.

Here is a truncated sample of this data:

`json5 { "version": "2021a", "years": "1800-2088", "deltaTs": "69.36 69.36 69.45", "leapSeconds": "912 1096 1461 1826 2191 2557 2922 3287 3652 4199 4564 4929 5660 6574 7305 7670 8217 8582 8947 9496 10043 10592 13149 14245 15522 16617 17167", "Africa/Abidjan": "-001608 +0000 0;-g.8/0/LMT 0/0/GMT;1;-2ldXH.Q;;48e5;BFCIGMGNMLMRSHSLSNTG", "Africa/Accra": "-000052 +0000 0;-0.Q/0/LMT 0/0/GMT k/k u/0 u/u;1212121212121212121212121212121212121212121212131414141414141;-2bRzX.8 9RbX.8 fdE 1BAk MLE 1Bck MLE 1Bck MLE 1Bck MLE 1BAk MLE 1Bck MLE 1Bck MLE 1Bck MLE 1BAk MLE 1Bck MLE 1Bck MLE 1Bck MLE 1BAk MLE 1Bck MLE 1Bck MLE 1Bck MLE 1BAk MLE 1Bck MLE 1Bck MLE 1Bck MLE Mok 1BXE M0k 1BXE fak 9vbu bjCu MLu 1Bcu MLu 1BAu MLu 1Bcu MLu 1Bcu MLu 1Bcu MLu;;41e5;GH", "Africa/Algiers": "+001212 +0100 0;c.c/0/LMT 9.l/0/PMT 0/0/WET 10/10/WEST 10/0/CET 20/10/CEST;1232323232323232454542423234542324;-3bQ0c.c MDA2.P cNb9.l HA0 19A0 1iM0 11c0 1oo0 Wo0 1rc0 QM0 1EM0 UM0 DA0 Imo0 rd0 De0 9Xz0 1fb0 1ap0 16K0 2yo0 mEp0 hwL0 jxA0 11A0 dDd0 17b0 11B0 1cN0 2Dy0 1cN0 1fB0 1cL0;;26e5;DZ", "Africa/Bissau": "-010220 +0000 0;-12.k/0/LMT -10/0 0/0/GMT;12;-2ldX0 2xoo0;;39e4;GW", "Africa/Cairo": "+020509 +0200 0;25.9/0/LMT 20/0/EET 30/10/EEST;1212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121212121;-2MBC5.9 1AQM5.9 vb0 1ip0 11z0 1iN0 1nz0 12p0 1pz0 10N0 1pz0 16p0 1jz0 s3d0 Vz0 1oN0 11b0 1oO0 10N0 1pz0 10N0 1pb0 10N0 1pb0 10N0 1pb0 10N0 1pz0 10N0 1pb0 10N0 1pb0 11d0 1oL0 11d0 1pb0 11d0 1oL0 11d0 1oL0 11d0 1oL0 11d0 1pb0 11d0 1oL0 11d0 1oL0 11d0 1oL0 11d0 1pb0 11d0 1oL0 11d0 1oL0 11d0 1oL0 11d0 1pb0 11d0 1oL0 11d0 1WL0 rd0 1Rz0 wp0 1pb0 11d0 1oL0 11d0 1oL0 11d0 1oL0 11d0 1pb0 11d0 1qL0 Xd0 1oL0 11d0 1oL0 11d0 1pb0 11d0 1oL0 11d0 1oL0 11d0 1ny0 11z0 1o10 11z0 1o10 11z0 1o10 11z0 1qN0 11z0 1o10 11z0 1o10 11z0 1o10 11z0 1o10 11z0 1qN0 11z0 1o10 11z0 1o10 WL0 1qN0 Rb0 1wp0 On0 1zd0 Lz0 1EN0 Fb0 c10 8n0 8Nd0 gL0 e10 mn0;;15e6;EG",

// ...

"US/Samoa": "Pacific/Pago_Pago", "UTC": "Etc/UTC", "Universal": "Etc/UTC", "W-SU": "Europe/Moscow", "Zulu": "Etc/UTC" }`

A detailed explanation of this format can be found at the end of this document.

The following options can be specified to tailor the output for your specific needs:

`typescript enum TzFormat { BINARY, JSON, JAVASCRIPT, TYPESCRIPT, TEXT } enum TzPresets { NONE, SMALL, LARGE, LARGE_ALT } enum TzPhase { DOWNLOAD, EXTRACT, PARSE, COMPILE, VALIDATE, REENCODE, OUTPUT_OF_RESULTS, DONE } enum TzMessageLevel { INFO, LOG, WARN, ERROR }

type TzCallback = ( phase?: TzPhase, level?: TzMessageLevel, message?: string, step?: number, stepCount?: number ) => void;

interface TzOptions { callback?: TzCallback, filtered?: boolean; fixRollbacks?: boolean; format?: TzFormat includeLeaps?: boolean, maxYear?: number; minYear?: number; mode?: TzMode; noBackward?: boolean; packrat?: boolean; preset?: TzPresets; roundToMinutes?: boolean; singleZone?: string; systemV?: boolean; urlOrVersion?: string; zoneInfoDir?: string; }`

• callback: This is an optional callback, used to provide information on the progress of parsing, compiling, and processing timezone data.

• filtered: When true, various obsolete timezones are omitted, such as America/Knox_IN, and the various Etc timezones.

fixRollbacks: It can be challenging enough when handling Daylight Saving Time (DST) that wall clock time can go backward during the course of a day. There are a few shifts in UTC offsets for some timezones, however, where even the calendar date goes backward, such as a case where the date/time is the 19th of the month, then it’s the 18th, and then it’s the 19th again, as happens with the unmodified America/Juneau timezone during October 1867.

The fixRollbacks option adjusts such transitions so that they delayed just enough to avoid backtracking of local calendar dates.

• minYear and maxYear: This is the range of years covered by the generated data, and it defaults to 1850-2050. Reducing the range can reduce generated data size, particularly when the lower limit is raised closer to current times, as many differently-named timezones share common descriptions when earlier historical transitions are omitted.

When the generated data is used by @tubular/time, a reduced range does not necessarily eliminate this utility of the output outside that range. It simply makes early times dependent on JavaScript Intl support (when available), and future times reliant on rules-based descriptions of Daylight Saving Time transitions.

For a few timezones rules-based descriptions are not possible for covering future times, as these timezones are reliant on rules which that cannot be expressed in the tz database short of explicitly providing specific DST transition dates and times for each future year. This is the case, for example, when transitions are based on Islamic calendar dates. In such cases DST transitions are reliable only up to maxYear.

• mode: One of three values, TzMode.REARGUARD, TzMode.MAIN, TzMode.VANGUARD, with TzMode.MAIN being the default. As of release 2021a, VANGUARD and REARGUARD are the same, providing negative DST support and DST rules with hours greater than 24. Selecting TzMode.REARGUARD will build timezone data without these features.

The future of these separate modes is uncertain, and they are likely to be phased out. It is at least possible, however, that sometime in the future VANGUARD mode might enable access to features not supported in MAIN.

• noBackward: If true, timezones aliases defined in the backward file are omitted.

• packrat: If true, extra timezone information defined in the backzone file is included.

• preset: One of four values, TzPresets.NONE, TzPresets.SMALL, TzPresets.LARGE, TzPresets.LARGE_ALT, with TzPresets.NONE being the defaults.

- TzPresets.NONE: No default options are changed. -TzPresets.SMALL: This covers explicitly-defined timezone information for the current year +/- five years, supplemented by rules-based extensions (i.e. knowing that for a particular timezone, say, “DST starts on the last Sunday of March and ends on the last Sunday of October”), and further supplemented by information extracted from Intl, when available. In JSON, JavaScript, or TypeScript form, this option currently generates about 40K of data. As option values, this is equivalent to:{ minYear: currentYear - 5, maxYear: currentYear + 5, options.systemV: true }-TzPresets.LARGE: Default option are set to cover full IANA timezone database up to 67 years beyond the current year. Using this will generate about 280K of data. As option values, this is equivalent to:{ minYear: 1800, maxYear: currentYear + 67, options.systemV: true }-TzPresets.LARGE_ALT: The same as TzPresets.LARGE, except with filtered, fixRollbacks, and roundToMinutes set to true. Using this will also generate about 280K of data.

• roundToMinutes: If true, UTC offsets which are not in whole minutes are rounded to the nearest minute.

• singleRegionOrZone: Normally all timezones are processed at once. You can, however, generate data for just a single timezone by specifying the name of that timezone with this option, or you can specify a region such as 'africa' or 'southamerica' to get all the timezones for just that region.

• systemV: If true, timezones defined in the systemv file are included.

• urlOrVersion: If left undefined or null, the latest tz database will be downloaded automatically from . Otherwise, a particular tz database version can be specified, such as '2021a', or a URL (including file URLs) can be used to specify a particular .tar.gz source file.

• zoneInfoDir: This option is for validating this tool’s parsing and compilation against zoneinfo/zic binaries located at the given directory path.

`$3`

async function writeTimezones(options: TzOutputOptions = {}): Promise

This function writes out timezone data in one of various text formats, or as zoneinfo/zic binaries. It includes all the options available for getTzData(), plus the following options:

`typescript interface TzOutputOptions extends TzOptions { bloat?: boolean; directory?: string; fileStream?: NodeJS.WriteStream, includeLeaps?: boolean, }`

• bloat: For binary output only, this option is equivalent to the zic option --bloat fat when true, the default being false, equivalent to --bloat slim.

• directory: For binary output only, this option specifies the path to the root directory where binaries will be stored, using a directory tree structure based on timezone names. The default is zoneinfo in the current working directory. Separate files are created for each timezone, in a structure like this:

`text ├── zoneinfo │ ├── Africa │ │ ├── Abidjan │ │ ├── Accra │ │ ├── Addis_Ababa │ │ ├── Algiers ••• │ ├── America │ │ ├── Adak │ │ ├── Anchorage │ │ ├── Anguilla │ │ ├── Antigua │ │ ├── Araguaina │ │ ├── Argentina │ │ │ ├── Buenos_Aires │ │ │ ├── Catamarca │ │ │ ├── ComodRivadavia │ │ │ ├── Cordoba ••• │ ├── Cuba │ ├── EET │ ├── EST │ ├── EST5EDT │ ├── Egypt │ ├── Eire │ ├── Etc │ │ ├── GMT │ │ ├── GMT+0 │ │ ├── GMT+1 │ │ ├── GMT+10 ••• │ ├── UTC │ ├── Universal │ ├── W-SU │ ├── WET │ └── Zulu`

• fileStream: For textual output only, this option specifies the output stream. If not specified, output is sent to stdout.

• format: One of TzFormat.BINARY, TzFormat.JSON, TzFormat.JAVASCRIPT, TzFormat.TYPESCRIPT, or TzFormat.TEXT, with the default being TzFormat.JSON.

JSON output is as shown in the previous example. JavaScript output is essentially the same, but declared as a module, with single-quoting for strings and some explanatory comments added. TypeScript output is in turn much like JavaScript, but uses export module syntax.

TzFormat.TEXT produces a somewhat human-readable list of transition times, possibly augmented with DST rules and meta info. Each transition is described with a before-and-after date, wall clock time for the transition, UTC offset, and DST offset. For example:

`text -------- America/New_York -------- ____-__-__ __:__:__ ±______ ±______ --> ____-__-__ __:__:__ -045602 +000000 LMT 1883-11-18 12:03:57 -045602 +000000 --> 1883-11-18 12:00:00 -050000 +000000 EST 1918-03-31 01:59:59 -050000 +000000 --> 1918-03-31 03:00:00 -040000 +010000 EDT* 1918-10-27 01:59:59 -040000 +010000 --> 1918-10-27 01:00:00 -050000 +000000 EST 1919-03-30 01:59:59 -050000 +000000 --> 1919-03-30 03:00:00 -040000 +010000 EDT* 1919-10-26 01:59:59 -040000 +010000 --> 1919-10-26 01:00:00 -050000 +000000 EST 1920-03-28 01:59:59 -050000 +000000 --> 1920-03-28 03:00:00 -040000 +010000 EDT* ••• 2049-11-07 01:59:59 -040000 +010000 --> 2049-11-07 01:00:00 -050000 +000000 EST 2050-03-13 01:59:59 -050000 +000000 --> 2050-03-13 03:00:00 -040000 +010000 EDT* 2050-11-06 01:59:59 -040000 +010000 --> 2050-11-06 01:00:00 -050000 +000000 EST Final Standard Time rule: US: 2007 to +inf, first Sun on/after Nov 1, at 2:00 wall time begin std time, S Final Daylight Saving Time rule: US: 2007 to +inf, first Sun on/after Mar 8, at 2:00 wall time save 60 mins, D Population: 21000000 Countries: US`

A trailing asterisk * indicates a transition into Daylight Saving Time.

• includeLeaps: This option adds leap second information to binary output files. Leap seconds are always included in the JSON, JavaScript, and TypeScript formats regardless of this option.

`Listing available tz database releases`

async function getAvailableVersions(): Promise

This function returns a sorted list of tz database release versions, the last of which will be the latest release available from .

@tubular/time `data format`

This variety of timezone data takes the form of an object with string keys and string values, where each key is either the name of a piece of metadata describing the collection of timezones, or the name of an IANA timezone.

Each timezone name is a key to a full timezone description, a simple alias to another timezone, or an alias to another timezone with some variant metadata.

To repeat the sample data from earlier in this document:

// ...

"US/Samoa": "Pacific/Pago_Pago", "UTC": "Etc/UTC", "Universal": "Etc/UTC", "W-SU": "Europe/Moscow", "Zulu": "Etc/UTC" }`

The only current metadata keys are deltaTs, leapSeconds, version, and years. If any new metadata keys are ever added they will be prefixed with an underscore (_). Every other key is the name of an IANA timezone.

• version: The tz database release version. •years: The range of years covered by explicit UTC offset transition times. •deltaTs: Starting at the year 2020, with one entry per year, the value of “delta T” at the start of each year. Delta T is the difference between UT1 and TDT (Terrestrial Dynamic Time), also the same as the difference between UT1 and TAI (International Atomic Time) plus 32.184 seconds. •leapSeconds: This is a list of days, specified as a number of days after January 1, 1970, for which a leap seconds has been added in the second just before the start of the specified day. If a number is negative, the absolute value of that number is the number of days after January 1, 1970, when a negative leap second has just occurred.

`$3`

#### Base-60 numbers

For compactness, many of the values in @tubular/time timezone descriptions are represented in base 60. The digit values used are as follows:

0-9: 0-9 a-z: 10-35 A-X: 36-59

These numbers can be negative, and they can also be fractional with the use of a “decimal” point. For all the values expressed at present, whole numbers are minutes, and the first digit after the “decimal” point is seconds. For example, -g.8 means negative 16 minutes, 8 seconds.

#### Not-entirely-formal Extended BNF for timezone description syntax


<time_zone> = <basics> ";" <local_time_type> { space <local_time_type> }
              [ ";" { <ltt_index_60> }
                [ ";" { <transition_delta> }
                  [ ";" [ <dst_rules> ]
                    [ ";" [ <population> ]
                      [ ";" [ <country_list> ] ] ] ] ] ]
<basics> = <initial_utc_offset> space <current_std_utc_offset> space <current_dst_offset>
<initial_utc_offset> = ( "+" | "-" ) ( hhmm | hhmmss )
     (i.e. decimal hours, minutes, and possibly seconds)
<current_std_utc_offset> = ( "+" | "-" ) ( hhmm | hhmmss )
<current_dst_offset> = [ "-" ] minutes (0 if DST is not currently observed)
<local_time_type> = <utc_offset_60> "/" <dst_offset_60> [ "/" <abbreviation> ]
<utc_offset_60> = Signed base-60 UTC offset, generally positive for east longitude,
     negative for west longitude.
<utc_offset_60> = Signed base-60 DTS offset, 0 when DST is not in effect.
<abbreviation> = Abbreviation, such as “GMT” or “EDT”, for the local time type.
<ltt_index_60> = 1-based base-60 index into local time types for each corresponding transition.
     The first index indicates the initial state of the timezone.
     The second index corresponds to the first listed <transition_delta>.
     The third index corresponds to the second listed <transition_delta>, etc.
<transition_delta> = The first <transition_delta> is a delta from 0, making it an
     absolute time value (in seconds from the 1970-01-01 UTC epoch) when the first
     timezone transition takes place. Each subsequent value is the number of seconds
     after the previous transition when the next transition takes place.
<dst_rules> = See the function toCompactTailRule() in the file tz-rule.ts for more on
     this format.
<population> = Approximate population of area covered by this timezone.
<country_list> = List of ISO Alpha-2 country codes for countries covered by this timezone.

#### Simple timezone alias

Example: 'America/Cayman': 'America/Panama',

Here America/Cayman is the alias, and America/Panama is the original.

#### Pseudo-alias

Example: 'America/Indianapolis': '!America/New_York',

America/Indianapolis is not a true alias of America/New_York, but in this particular instance, America/Indianapolis has an identical timezone description which can be shared.

#### Modified pseudo-alias

Example: 'Atlantic/South_Georgia': '!30,GS,America/Noronha',

Here Atlantic/South_Georgia shares a timezone description with America/Noronha`, but with modified metadata for population and country list.