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refactor: resolve the time scales of DateTime from the epoch module in time module in @observerly/astrometry #551

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Merged
michealroberts merged 1 commit into from
Sep 3, 2026
Merged

refactor: resolve the time scales of DateTime from the epoch module in time module in @observerly/astrometry #551

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34 changes: 13 additions & 21 deletions src/time.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,12 @@

/*****************************************************************************************************************/

import { getJulianDate, getModifiedJulianDate } from './epoch'
import {
getInternationalAtomicTime,
getJulianDate,
getModifiedJulianDate,
getTerrestrialTime
} from './epoch'

import { LEAP_SECONDS } from './iers'

Expand Down Expand Up @@ -48,24 +53,12 @@ export class DateTime extends Date {
*
*/
getInternationalAtomicTime(): number {
const zero = new Date('1972-01-01T00:00:00.000+00:00').getTime()
// The International Atomic Time (TAI) is the time scale that combines the output of
// some 400 highly precise atomic clocks worldwide, and provides the exact speed of our
// clocks, which is essential for the accurate positioning of satellites and for many
// other applications.
let dtai = 0

const d = super.getTime()

// If the date is before the first leap second was added, return the date.
if (d < zero) return d

// Iterate backwards over the leap seconds table to find the current number of leap seconds.
dtai = applyDTAICorrectionToDateTime(d, zero)

// The difference between TAI and UTC is the number of leap seconds that have been
// added to the UTC time scale. This difference is known as DTAI.
return d + dtai * 1000
// other applications. The time scale itself is resolved by the epoch module, so that
// the leap seconds are applied in one place:
return getInternationalAtomicTime(this).getTime()
}

/**
Expand All @@ -83,11 +76,10 @@ export class DateTime extends Date {
*
*/
getTerrestrialTime(): number {
const tai = this.getInternationalAtomicTime()

// The difference between TAI and TT is the number of leap seconds that have been
// added to the UTC time scale. This difference is known as DTAI.
return tai + 32.184 * 1000
// The Terrestrial Time (TT) is the International Atomic Time (TAI) displaced by the
// constant 32.184 seconds. The time scale itself is resolved by the epoch module, so
// that the displacement is applied in one place:
return getTerrestrialTime(this).getTime()
}

/**
Expand Down