Enhancement of Date class with better timezone support
npm install timezone-date.tsEnhancement of Date class with better timezone support.



- Compliant to Date methods
- Allow changing timezone anytime
- Support both numeric timezone offsets and IANA timezone identifiers (e.g., "America/New_York")
- Automatic Daylight Saving Time (DST) handling with IANA timezones
- Typescript support
- Tiny code base (below 1KB minizipped)
Jump between timezones:
``typescript
import { TimezoneDate } from 'timezone-date.ts'
const d = TimezoneDate.fromDate(new Date('2020-04-21T10:00:00.000Z'))
d.timezone = 0
d.getHours() // 10
d.timezone = +8
d.getHours() // 18
d.getTimezoneOffset() // -480 (in mintes, same format as Native Date)
d.setHours(9)
d.timezone++
d.getHours() // 10
d.toLocaleTimeString() // '10:00:00 AM'
`
Set a specific time (e.g. from UI input)
`typescript`
let date = new TimezoneDate()
date.timezone = +8
date.setFullYear(2020, 11 - 1, 28)
date.setHours(9, 2, 38)
console.log(date.toString()) // Sat Nov 28 2020 09:02:38 GMT+0800 (Hong Kong Standard Time)
Using IANA timezone identifiers with automatic DST handling:
`typescript
import { TimezoneDate } from 'timezone-date.ts'
let date = new TimezoneDate()
date.timezone = 'America/New_York' // IANA timezone identifier
// Summer time (EDT, UTC-4)
date.setTime(new Date('2025-06-01T12:00:00Z').getTime())
date.getTimezoneOffset() / 60 // -4 (EDT)
date.toLocaleString('en-US') // "6/1/2025, 8:00:00 AM"
// Winter time (EST, UTC-5)
date.setTime(new Date('2025-12-01T12:00:00Z').getTime())
date.getTimezoneOffset() / 60 // -5 (EST)
date.toLocaleString('en-US') // "12/1/2025, 7:00:00 AM"
`
Using the exported utility function:
`typescript
import { getTimezoneOffsetForIANA } from 'timezone-date.ts'
const time = new Date('2025-06-01T12:00:00Z').getTime()
const offset = getTimezoneOffsetForIANA('America/New_York', time)
console.log(offset) // -4 (hours, EDT in summer)
`
`bash`
npm i timezone-date.ts
`typescript
import { TimezoneDate } from 'timezone-date.ts'
/ custom timezone (numeric offset) /
new TimezoneDate(Date.now(), { timezone: +8 })
/ custom timezone (IANA identifier) /
new TimezoneDate(Date.now(), { timezone: 'America/New_York' })
/ default timezone (in the environment) /
new TimezoneDate() // current time
new TimezoneDate(Date.now())
TimezoneDate.fromTime(Date.now())
TimezoneDate.fromDate(new Date())
TimezoneDate.from(Date.now()) // from Date or timestamp
`
The timezone property accepts:
- Numeric offset (in hours): +8, -5, 0, etc."America/New_York"
- Fixed offset, does not handle DST automatically
- IANA timezone identifier: , "Asia/Hong_Kong", "Europe/London", etc.
- Automatically handles Daylight Saving Time (DST)
- Uses the browser's/Node.js's built-in timezone database
Get the timezone offset in hours for a given IANA timezone identifier at a specific time.
`typescript
import { getTimezoneOffsetForIANA } from 'timezone-date.ts'
const time = new Date('2025-06-01T12:00:00Z').getTime()
const offset = getTimezoneOffsetForIANA('America/New_York', time)
// Returns -4 (EDT in summer) or -5 (EST in winter)
``
This is free open sourced software (FOSS), with BSD 2-Clause License