T8 Date Format

Locale-agnostic date formatting utilities

This package doesn't seek to contain the knowledge about the specific locale-dependent date formats, but provides a flexible and concise way to construct them.

Installation: npm i @t8/date-format

Static templates

import { formatDate } from "@t8/date-format";

formatDate(new Date(), "{YYYY}-{MM}-{DD} {HH}:{mm}:{ss}");
// 2022-07-19 12:34:56

Dynamic templates

import { formatDate } from "@t8/date-format";

let eraTemplate = ({ E }) => E === 1 ? "AD {YE}" : "{YE} BC";
// {YE} stands for the unsigned year of a calendar era

formatDate("2022-07-19", eraTemplate);
// AD 2022

formatDate(-62200000000000, eraTemplate);
// 3 BC

import { formatDate } from "@t8/date-format";

let weekDays = "Sun Mon Tue Wed Thu Fri Sat".split(" ");
let months = "Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec".split(" ");

let shortDateFormat = {
  template: "{WD}, {MMM} {D}",
  transform: {
    WD: ({ weekDay }) => weekDays[weekDay],
    MMM: ({ month }) => months[month],
  },
};

formatDate("2022-12-02T12:34:56.789", shortDateFormat);
// Fri, Dec 2

Custom locale definition

import { formatDate } from "@t8/date-format";
import { customLocale } from "./customLocale";

formatDate(new Date(), customLocale.fullDate);
// þriðjudagur 19. júlí 2022

formatDate(new Date(), customLocale.shortDate);
// 19.07.2022

const customWeekDays = [
  "sunnudagur",
  "mánudagur",
  "þriðjudagur",
  "miðvikudagur",
  "fimmtudagur",
  "föstudagur",
  "laugardagur",
];

const customMonths = [
  "janúar",
  "febrúar",
  "mars",
  "apríl",
  "maí",
  "júní",
  "júlí",
  "ágúst",
  "september",
  "október",
  "nóvember",
  "desember",
];

export const customLocale = {
  shortDate: "{DD}.{MM}.{Y}",
  fullDate: {
    template: "{WD} {D}. {MMM} {Y}",
    transform: {
      WD: ({ weekDay }) => customWeekDays[weekDay],
      MMM: ({ month }) => customMonths[month],
    },
  },
};

Durations

import { formatDuration } from "@t8/date-format";

formatDuration(123456);
// 2"03.456"

List of date placeholders

Placeholder	Value
{Y}	Year
{YY}	Year, zero-prefixed when shorter than 2 digits
{YYYY}	Year, zero-prefixed when shorter than 4 digits
{yy}	Year, last 2 digits zero-prefixed when shorter than 2 digits
{YE}	Year of a calendar era (specified by AD/BC or CE/BCE)
{E}	Christian era: 1 for AD, -1 for BC
{CE}	Common Era: 1 for CE, -1 for BCE
{M}	Month
{MM}	Month, zero-prefixed when shorter than 2 digits
{D}	Day
{DD}	Day, zero-prefixed when shorter than 2 digits
{H}	Hours
{HH}	Hours, zero-prefixed when shorter than 2 digits
{h}	12h-clock hours
{hh}	12h-clock hours, zero-prefixed when shorter than 2 digits
{a}	Day period: AM/PM
{m}	Minutes
{mm}	Minutes, zero-prefixed when shorter than 2 digits
{s}	Seconds
{ss}	Seconds, zero-prefixed when shorter than 2 digits
{ms}	Milliseconds, zero-prefixed when shorter than 3 digits
{tz}	Time zone
{iso}	Local time zone ISO date string
{isoDate}	Date (= {YYYY}-{MM}-{DD})
{isoTime}	Time (= {HH}:{mm}:{ss})
{isoTimeMs}	Time with milliseconds

The following unformatted date components are also available as placeholder values: timestamp, year, month, day, hours, hours12 (12h-clock hours), minutes, seconds, milliseconds, weekDay, timezoneOffset, input (the first argument of the formatDate() call).