date

Note

This is one of 199 standalone projects, maintained as part of the @thi.ng/umbrella monorepo and anti-framework.

🚀 Please help me to work full-time on these projects by sponsoring me on GitHub. Thank you! ❤️

• About
• Status
• Installation
• Dependencies
• Usage examples
• API
  • DateTime
  • Math & comparison
  • Iterators
  • Relative dates
    • Parsing
    • Formatting
  • Date & time formatters
  • Timecodes
  • Locales
• Authors
• License

About

Datetime types, relative dates, math, iterators, composable formatters, locales.

Status

STABLE - used in production

Search or submit any issues for this package

Installation

yarn add @thi.ng/date

ESM import:

import * as date from "@thi.ng/date";

Browser ESM import:

<script type="module" src="https://esm.run/@thi.ng/date"></script>

JSDelivr documentation

For Node.js REPL:

const date = await import("@thi.ng/date");

Package sizes (brotli'd, pre-treeshake): ESM: 5.42 KB

Dependencies

• @thi.ng/api
• @thi.ng/checks
• @thi.ng/strings

Note: @thi.ng/api is in most cases a type-only import (not used at runtime)

Usage examples

Five projects in this repo's /examples directory are using this package:

Screenshot	Description	Live demo	Source
	Heatmap visualization of this mono-repo's commits		Source
	CSP channel-based event handling, async transducers & reactive UI components	Demo	Source
	Mastodon API feed reader with support for different media types, fullscreen media modal, HTML rewriting	Demo	Source
	Live coding playground for 2D geometry generation using @thi.ng/pointfree-lang	Demo	Source
	Zig-based To-Do list, DOM creation, local storage task persistence	Demo	Source

API

Generated API docs

TODO - Please see tests and doc strings in source for now...

DateTime

The DateTime class acts as a thin wrapper around UTC epochs/timestamps, with the constructor supporting coercions and varying granularity/precision (from years to milliseconds). Default precision is milliseconds.

Key	Precision
y	Year
M	Month
d	Day
h	Hour
m	Minute
s	Second
t	Millisecond

Note: DateTime instances also define the above keys as properties, plus getters for week-in-year (.w) and quarter (.q).

import { dateTime } from "@thi.ng/date";

// create w/ current date (or pass epoch, string, Date or DateTime instances)
const a = dateTime();
// DateTime { y: 2020, M: 8, d: 19, h: 12, m: 17, s: 16, t: 884 }

// provide additional precision (here year only)
const b = dateTime(a, "y");
// or
const b = a.withPrecision("y")
// DateTime { y: 2020, M: 0, d: 1, h: 0, m: 0, s: 0, t: 0 }

a.toString();
// Sat Sep 19 2020 12:17:16 GMT'
a.toISOString()
// '2020-09-19T12:17:16.884Z'

b.toISOString();
// 2020-01-01T00:00:00.000Z

a.isLeapYear()
// true

a.daysInMonth()
// 30

a.dayInYear()
// 263

a.weekInYear()
// 38

a.isAfter(b)
// true\

b.isBefore(a)
// true

Math & comparison

DateTime instances support basic math to derive future/past instances, given an offset period. Period identifiers are any Precision ID (see above) or w (week, aka 7 days) or q (quarter, aka 3 months):

import { dateTime, difference, absDifference, asDays } from "@thi.ng/date";

const a = dateTime();
// DateTime { y: 2020, M: 8, d: 19, h: 12, m: 17, s: 16, t: 884 }

// create new instance 61 seconds in the future
// any `Period` ID can be used
a.add(61, "s")
// DateTime { y: 2020, M: 8, d: 19, h: 12, m: 18, s: 17, t: 884 }

// ...or 90 days ago
a.add(-90, "d")
// DateTime { y: 2020, M: 5, d: 21, h: 12, m: 17, s: 16, t: 884 }

// ...or 2 quarters (aka 2x 3 months) ahead of time
a.add(2, "q").toISOString()
// "2021-03-19T12:17:16.884Z"

// check for equivalence
a.equiv("2020-09-19T12:17:16.884Z")
// true

// are dates equal (with tolerance of ±100 ms)
a.eqDelta(a.add(99, "t"), 100)
// true

a.compare(a.add(1, "s"))
// -1000

// compute (signed) difference between dates (in milliseconds)
difference(a, "1970-01-01") === a.getTime()
// true

// difference = a - b
difference("2020-02", "2021-02")
// -31622400000

// always produces unsigned result
absDifference("2020-02", "2021-02")
// 31622400000

// compute abs difference in days
asDays(absDifference("2020-02", "2021-02"))
// 366 (because 2020 was a leap year)

Iterators

Several iterators are provided to produce timestamps of various granularities between two given dates. Originally, these were intended for visualization purposes (i.e. as axis tick label generators for @thi.ng/viz).

• years()
• querters()
• months()
• weeks()
• days()
• hours()
• minutes()
• seconds()
• milliseconds()

import { months, FMT_yyyyMMdd } from "@thi.ng/date";

[...months("2021-01-03", "2021-07-16")]
// [
//   1609459200000,
//   1612137600000,
//   1614556800000,
//   1617235200000,
//   1619827200000,
//   1622505600000,
//   1625097600000
// ]

[...months("2021-01-03", "2021-07-16")].map((x) => FMT_yyyyMMdd(x))
// [
//   '2021-02-01',
//   '2021-03-01',
//   '2021-04-01',
//   '2021-05-01',
//   '2021-06-01',
//   '2021-07-01'
// ]

Relative dates

Parsing

Relative dates can be obtained via parseRelative() or relative().

import { dateTime, parseRelative } from "@thi.ng/date";

const now = dateTime();
// DateTime { y: 2021, M: 2, d: 21, h: 14, m: 26, s: 0, t: 661 }

// see the linked documentation for all supported formats
parseRelative("2 weeks ago", now);
// DateTime { y: 2021, M: 2, d: 7, h: 14, m: 26, s: 0, t: 661 }

parseRelative("an hour", now);
// DateTime { y: 2021, M: 2, d: 21, h: 15, m: 26, s: 0, t: 661 }

parseRelative("tomorrow", now);
// DateTime { y: 2021, M: 2, d: 22, h: 14, m: 26, s: 0, t: 661 }

parseRelative("-1 month", now)
// DateTime { y: 2021, M: 1, d: 21, h: 14, m: 26, s: 0, t: 661 }

Formatting

Dates can be formatted as relative descriptions using formatRelative() and formatRelativeParts(). Both functions use the currently active locale and accept an optional reference date (default: now()).

import {
    setLocale, withLocale, DE_LONG, EN_LONG,
    formatRelative, formatRelativeParts, formatDuration,
    decomposeDifference
} from "@thi.ng/date";

setLocale(EN_LONG);

formatRelative("2020-06-01", "2021-07-01")
// "1 year ago"
formatRelative("2020-08-01", "2021-07-01")
// "11 months ago"
formatRelative("2021-07-01 13:45", "2021-07-01 12:05")
// "in 2 hours"
formatRelative("2021-07-01 12:23:24", "2021-07-01 12:05")
// "in 18 minutes"

// with default precision (seconds)
formatRelativeParts("2012-12-25 17:59:34", "2021-07-16 12:05")
// "8 years, 6 months, 21 days, 17 hours, 5 minutes, 26 seconds ago"

// with day precision
formatRelativeParts("2012-12-25 17:59:34", "2021-07-16 12:05", "d")
// "8 years, 6 months, 22 days ago"

// with month precision
formatRelativeParts("2012-12-25 17:59:34", "2021-07-16 12:05", "M")
// "8 years, 7 months ago"

formatRelativeParts("2021-07-16", "2021-01-01", "y")
// "in less than 1 year"

// with locale DE_LONG
withLocale(DE_LONG, () => formatRelativeParts("2020-01-01 12:34"))
// "vor 1 Jahr, 6 Monaten, 15 Tagen, 23 Stunden, 38 Minuten, 9 Sekunden"

// obtain the relative parts in raw form
// returns tuple of: [sign, years, months, days, hours, mins, secs, millis]
decomposeDifference("2020-01-01 12:34", Date.now())
// [-1, 1, 6, 15, 23, 38, 9, 703]

// format a duration (in ms), optionally with given precision
formatDuration(45296000)
// "12 h, 34 min, 56 s"

formatDuration(45296000, "h")
// "13 h"

formatDuration(45296000,"d")
// "< 1 d"

Date & time formatters

Custom date/time formatters can be assembled via defFormat(), using the following partial format identifiers. The MMM and E formatters use the currently active locale. To escape a formatter and use as a string literal, prefix the term with \\.

ID	Description
yy	Short year (2 digits)
yyyy	Full year (4 digits)
M	Unpadded month
MM	Zero-padded 2-digit month
MMM	Month name in current locale (e.g. Feb)
d	Unpadded day of month
dd	Zero-padded 2-digit day of month
E	Weekday name in current locale (e.g. Mon)
w	Unpadded week-in-year (ISO8601)
ww	Zero-padded 2-digit week-in-year (ISO8601)
q	Unpadded quarter
H	Unpadded hour of day (0-23)
HH	Zero-padded 2-digit hour of day (0-23)
h	Unpadded hour of day (1-12)
m	Unpadded minute of hour
mm	Zero-padded 2-digit minute of hour
s	Unpadded second of minute
ss	Zero-padded 2-digit second of minute
S	Unpadded millisecond of second
SS	Zero-padded 3-digit millisecond of second
A	12-hour AM/PM marker (uppercase)
a	12-hour am/pm marker (lowercase)
Z	Timezone offset in signed ±HH:mm format
ZZ	Same as Z, but special handling for UTC
/ED	Locale-specific weekday-day separator
/DM	Locale-specific day-month separator
/MY	Locale-specific month-year separator
/HM	Locale-specific hour-minute separator

(Format IDs somewhat based on Java's SimpleDateFormat)

The following preset formatters are available:

• FMT_ISO - "2020-09-13T21:42:07.123Z"
• FMT_ISO_SHORT - "2020-09-13T21:42:07Z"
• FMT_yyyyMMdd - "2020-09-13"
• FMT_yyyyMMdd_ALT - "20200913"
• FMT_Mdyyyy - "9/13/2020"
• FMT_MMMdyyyy - "Sep 13 2020"
• FMT_dMyyyy - "13/9/2020"
• FMT_dMMMyyyy - "13 Sep 2020"
• FMT_yyyyMMdd_HHmmss - 20200913-214207
• FMT_HHmm - "21:42"
• FMT_hm - "9:42 PM"
• FMT_HHmmss - "21:42:07"
• FMT_HHmmss_ALT - "214207"
• FMT_hms - "9:42:07 PM"
• FMT_yyyy - "2020" (4 digit year)
• FMT_MM - "12" (2 digit month)
• FMT_ww - "52" (2 digit week)
• FMT_dd - "28" (2 digit day in month)
• FMT_HH - "23" (2 digit hour, 24h system)
• FMT_mm - "59" (2 digit minute)
• FMT_ss - "01" (2 digit second)

All formatters are fully composable/nestable, i.e. new formats can be created using existing formats like so:

import { defFormat, FMT_HHmmss, FMT_yyyyMMdd } from "@thi.ng/date";

defFormat([FMT_yyyyMMdd, " @ ", FMT_HHmmss])();
// "2024-02-28 @ 12:05:47"

Timecodes

For timebased media applications, the higher-order defTimecode() can be used to create a formatter for a given FPS (frames / second, in [1..1000] range), e.g. HH:mm:ss:ff. The returned function takes a single arg (time in milliseconds) and returns formatted string.

The timecode considers days too, but only includes them in the result if the day part is non-zero. The 4 separators between each field can be customized via 2nd arg (default: all :).

import { defTimecode, DAY, HOUR, MINUTE, SECOND } from "@thi.ng/date";

const a = defTimecode(30);
a(1*HOUR + 2*MINUTE + 3*SECOND + 4*1000/30)
// "01:02:03:04"

a(DAY);
// "01:00:00:00:00"

const b = defTimecode(30, ["d ", "h ", "' ", '" ']);
b(DAY + HOUR + 2*MINUTE + 3*SECOND + 999)
// "01d 01h 02' 03" 29"

Locales

The following locale presets are available by default:

Preset	Example
DE_SHORT	29.6.2021 @ 5:48
DE_LONG	Dienstag, 29. Juni 2021 @ 5:48
EN_SHORT	29/06/2021 @ 5.48 am
EN_LONG	Tuesday 29 June 2021 @ 5.48 am
ES_LONG	martes 29 junio 2021 @ 5:48
FR_LONG	mardi 29 juin 2021 @ 5h 48
IT_LONG	martedì 29 giugno 2021 @ 5.48

The MMM (month) and E (weekday) formatters make use of the strings provided by the current LOCALE (default: EN_SHORT) and can be set/changed via the setLocale() function:

import {
    dateTime, defFormat, setLocale,
    EN_SHORT, EN_LONG
} from "@thi.ng/date";

const fmt = defFormat(["E", " ", "d", " ", "MMM", " ", "yyyy"]);

setLocale(EN_SHORT); // also the default
// {
//   months: [
//     'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
//     'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'
//   ],
//   days: [ 'Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat' ]
// }

fmt(dateTime());
// Sat 19 Sep 2020

setLocale(EN_LONG);

fmt(dateTime());
// Saturday 19 September 2020

Use withLocale() to only temporarily set a locale and execute a function with it, then automatically restoring the currently active locale.

import { dateTime, withLocale, FR_LONG } from "@thi.ng/date";

fmt(dateTime());
// 'Fri 16 Jul 2021'

withLocale(FR_LONG, () => fmt(dateTime()));
// 'vendredi 16 juillet 2021'

fmt(dateTime());
// 'Fri 16 Jul 2021'

Authors

• Karsten Schmidt

If this project contributes to an academic publication, please cite it as:

@misc{thing-date,
  title = "@thi.ng/date",
  author = "Karsten Schmidt",
  note = "https://thi.ng/date",
  year = 2020
}

License

© 2020 - 2024 Karsten Schmidt // Apache License 2.0