A lightweight javascript timezone library

calculate time in remote timezones
support daylight savings, leap years, and hemispheres
Moment-like 💘 API (but immutable!)
Orient time by quarter, season, month, week…
Zero Dependencies - (no Intl API)
only 43KB.

<script src="https://unpkg.com/spacetime"></script>
<script>
  var d = spacetime('March 1 2012', 'America/New_York')
  //set the time
  d = d.time('4:20pm')

  d = d.goto('America/Los_Angeles')
  d.time()
  //'1:20pm'
</script>

npm install spacetime

const spacetime = require('spacetime')
let d = spacetime.now('Europe/Paris')
d.dayName()
//'Wednesday'
d.isAsleep()
//true

Or with Typescript

import spacetime from 'spacetime'
let d = spacetime.now()
d.format('nice')
//'Apr 1st, 4:32pm'

make sure to add this to your tsconfig.json:

{
  "compilerOptions": {
    "esModuleInterop": true
  }
}

Demo • Full API

spacetime-geo • spacetime-informal • spacetime-daylight

spacetime-calendar • spacetime-week

Date Inputs:

//epoch
s = spacetime(1489520157124)

//array [yyyy, m, d] (zero-based months, 1-based days)
s = spacetime([2017, 5, 2])

//iso
s = spacetime('July 2, 2017 5:01:00')

// All inputs accept a timezone, as 2nd param:
s = spacetime(1489520157124, 'Canada/Pacific')
s = spacetime('2019/05/15', 'Canada/Pacific')

// or set the offset right in the date-string (ISO-8601)
s = spacetime('2017-04-03T08:00:00-0700')
// 'Etc/GMT-7'

// Some helpers
s = spacetime.now()
s = spacetime.today() // This morning
s = spacetime.tomorrow() // Tomorrow morning

Get & Set dates:

s.date() // 14
s.year() // 2017
s.season() // Spring
s = s.hour(5) // Change to 5am
s = s.date(15) // Change to the 15th
s = s.day('monday') // Change to (this week's) monday
s = s.month('march') // Change to (this year's) March 1st
s = s.quarter(2) // Change to April 1st
s.era() // 'BC'/'AD'
s.decade() // 2000
s.century() // 21

// Percentage-based information
s.progress().month = 0.23 // We're a quarter way through the month
s.progress().day = 0.48 // Almost noon
s.progress().hour = 0.99 // 59 minutes and 59 seconds

// Add/subtract methods
s = s.add(1, 'week')
s = s.add(3, 'quarters')
s = s.subtract(2, 'months').add(1, 'day')

// start-of/end-of
s = s.startOf('day') // 12:00am
s = s.startOf('month') // 12:00am, April 1st
s = s.endOf('quarter') // 11:59:59pm, June 30th

s = s.nearest('hour') //round up/down to the hour
s = s.nearest('quarter-hour') //5:15, 5:30, 5:45..
s = s.next('month') //start of the next month
s = s.last('year') //start of the last year

// fill-in all dates between a range
s.every('week', 'Jan 1st 2020') // (in tz of starting-date)

//utilities:
s.clone() // Make a copy
s.isValid() // Sept 32nd → false
s.isAwake() // it's between 8am → 10pm
s.json() // get values in every unit as key-val object

Comparisons:

let s = spacetime([2017, 5, 2])
let start = s.subtract(1, 'milliseconds')
let end = s.add(1, 'milliseconds')

// gt/lt/equals
s.isAfter(d) // True
s.isEqual(d) // False
s.isBefore(d) // False
s.isBetween(start, end, inclusive?) // True

// Comparison by unit
s.isSame(d, 'year') // True
s.isSame(d, 'date') // False
s.diff(d, 'day') // 5
s.diff(d, 'month') // 0

//make a human-readable diff
let before = spacetime([2018, 3, 28])
let now = spacetime([2017, 3, 28]) //one year later
now.since(before)
/* {
    diff: {
      years: 0,
      months: 11,
      days: 30,
      hours: 23,
      minutes: 59,
      seconds: 59
    },
    rounded: 'in 12 months',
    qualified: 'in almost 12 months',
    precise: 'in 11 months, 30 days'
  }
*/

it’s sometimes confusing how .diff() and .since() understand things:

spacetime('January 1 2017').diff('December 30 2016', 'year')
// returns 1
spacetime('January 1 2017').since('December 31 2016').diff
// returns {years:0, months:0, days:1}

Timezones:

// Roll into a new timezone, at the same moment
s = s.goto('Australia/Brisbane')

this is the safest way to declare a timezone, using an IANA name.

if you want to support more relaxed timezone names like 'EST', Eastern time, use spacetime-informal

s = s.goto('Jamaica') // "America/Jamaica"
s = s.goto('-7h') // UTC-7
s = s.goto('GMT+8') // -8h!
// (these should be used with some caution)

//list timezones by their \ time
spacetime.whereIts('8:30pm', '9:30pm') // ['America/Winnipeg', 'America/Yellowknife'... ]
spacetime.whereIts('9am') //(within this hour)

// Timezone metadata
s.timezone().name // 'Canada/Eastern' (either inferred or explicit)
s.hemisphere() // North
s.timezone().current.offset // -4 (in hours)
s.hasDST() // True
s.isDST() // True

//list all timezones
s.timezones

Date Formatting:

// Date + time formatting
s.format('time') // '5:01am'
s.format('numeric-uk') // 02/03/2017
s.format('month') // 'April'
s.format('month-short') // 'Apr'
s.format('month-pad') // '03'
s.format('iso-month') // '04'

//if you want more complex formats, use {}'s
s.format('{year}-{date-pad}-{month-pad}') // '2018-02-02'
s.format("{hour} o'clock") // '2 o'clock'
s.format('{time}{ampm} sharp') // '2:30pm sharp'

//if you prefer, you can also use unix-formatting
s.unixFmt('yyyy.MM.dd h:mm a') // '2017.Nov.16 11:34 AM'

Limitations & caveats

Historical timezone info

DST changes move around all the time, and timezones pop-in and out of existence. We store and use only the latest DST information, and apply it to historical dates.

DST changes within 1-hour

when very-close to a DST change, we can get the hour wrong, by 1.

This is a tricky order-of-operations issue.

To most people, DST changes occur during an unspecified time overnight, anyways.

International date line

.goto() never crosses the date-line. This is mostly the intuitive behaviour.

But if you’re in Fiji (just west of the date line), and you go to Midway (just east of the date line), .goto() will subtract a bunch of hours, instead of just adding one.

Destructive changes

if it’s 2:30pm and you add a month, it should still be 2:30pm. Some changes are more destructive than others. Many of thse choices are subjective, but also sensible.

0-based vs 1-based …

for better or worse we copy the JavaScript spec for 0-based months, and 1-based dates.

ISO-formatting is different, so keep on your toes.

see more considerations and gotchas

Options

Ambiguity warnings:

javascript dates use millisecond-epochs, instead of second-epochs, like some other languages. This is a common bug, and spacetime can warn if you set an epoch within January 1970. to enable:

let s = spacetime(123456, 'UTC', {
  silent: false
})
s.log() // "Jan 1st, 12:02am"

There is another situation where you may see a console.warn - if you give it a timezone, but then set a ISO-date string with a different offset, like 2017-04-03T08:00:00-0700 (-7hrs UTC offset). It sets the timezone to UTC-7, but also gives a warning.

let s = spacetime('2017-04-03T08:00:00-0700', 'Canada/Eastern', {
  silent: false
})
s.timezone().name // "Etc/GMT-7"

Configure ‘today’ context:

spacetime makes some assumptions about some string inputs:

// assumes start of month
let s = spacetime('June 1992')
s.date() // 1

// assumes current year
let s = spacetime('June 5th')
s.year() // 2020 (or whatever it is now)

// assumes Jan 1st
let s = spacetime('2030')
s.month() // 'January'

you can configure this assumed date (usually for testing) by passing it in as an option:

let today= {
  month: 3,
  date: 4,
  year: 1996,
}
let s = spacetime('June 5th', null, {today:today})
s.year() // 1996

it also works for spacetime.now(tz, {today:today}) and others.

Extending/Plugins:

you can throw any methods onto the Spacetime class you want, with spacetime.extend():

spacetime.extend({
  isHappyHour: function() {
    return this.hour() === 16
  }
})

let s = spacetime.now('Australia/Adelaide')
s.isHappyHour()
//false

s = s.time('4:30pm')
s.isHappyHour()
//true

DD/MM/YYY interpretation:

by default spacetime uses the American interpretation of ambiguous date formats, like javascript does:

spacetime('12/01/2018') //dec 1st

// unless it's clear (>12):
spacetime('13/01/2018') //jan 13th

you can change this behaviour by passing in a dmy option, like this:

spacetime('12/01/2018', null, { dmy: true }) //jan 12th

this format is more common in britain, and south america.

Custom languages:

a.i18n({
  days: {
    long: ['domingo', 'lunes', 'martes', 'miércoles', 'jueves', 'viernes', 'sábado'],
    short: ['dom', 'lun', 'mar', 'mié', 'jue', 'vie', 'sáb']
  },
  months: {
    long: [...],
    short: ['ene', 'feb', 'mar', 'abr', 'may', 'jun', 'jul', 'ago', 'sep', 'oct', 'nov', 'dic'],
  }
});
a.format('day') //'Sábado'

Configure start of week:

by default, the start of the week is monday.

You can determine the week by the official country setting, with spacetime-week

let s = spacetime.now()
s = s.weekStart('sunday')

s = s.startOf('week')
s.dayName()
//sunday

s = s.endOf('week')
s.dayName()
//saturday

Download Details:

Author: spencermountain

Demo: http://spacetime.how/

Source Code: https://github.com/spencermountain/spacetime

#javascript