Get moon phase by Date, written in TypeScript. Accurate from year 1900 to 2199 inclusive.

getMoonPhase.ts

export { EMoonPhase, EMoonPhaseName, MOON_PHASE_NAMES, moonPhase }


const { round, trunc: truncate } = Math


enum EMoonPhase {
  New = 0,
  WaxingCrescent,
  QuarterMoon,
  WaxingGibbous,
  Full,
  WaningGibbous,
  LastQuarter,
  WaningCrescent,
  COUNT = 8
}


enum EMoonPhaseName {
  New = 'New',
  WaxingCrescent = 'Waxing Crescent',
  QuarterMoon = 'Quarter Moon',
  WaxingGibbous = 'Waxing Gibbous',
  Full = 'Full',
  WaningGibbous = 'Waning Gibbous',
  LastQuarter = 'Last Quarter',
  WaningCrescent = 'Waning Crescent',
  COUNT = 'COUNT'
}


const MOON_PHASE_NAMES: EMoonPhaseName[] = [ // Look-up table.
  EMoonPhaseName.New,
  EMoonPhaseName.WaxingCrescent,
  EMoonPhaseName.QuarterMoon,
  EMoonPhaseName.WaxingGibbous,
  EMoonPhaseName.Full,
  EMoonPhaseName.WaningGibbous,
  EMoonPhaseName.LastQuarter,
  EMoonPhaseName.WaningCrescent,
  EMoonPhaseName.COUNT
]


// Reference: http://individual.utoronto.ca/kalendis/lunar/#FALC
// Also known as a synodic month.
// An average synodic month takes 29 days, 12 hours, 44 minutes, 3 seconds.
const LUNAR_CYCLE = 29.53058770576

const DAYS_PER_YEAR = 365.25
const DAYS_PER_MONTH = 30.6

// Number of days since known new moon on `1900-01-01`.
const DAYS_SINCE_NEW_MOON_1900_01_01 = 694039.09


interface IResult { name: EMoonPhaseName, phase: EMoonPhase }


// Ported from `http://www.voidware.com/moon_phase.htm`.
function moonPhase (date: Date = new Date()): IResult {

  // let year = date.getYear()
  let year: number = date.getFullYear()

  let month: number = date.getMonth()
  const day: number = date.getDay()

  if (month < 3) {
    year--
    month += 12
  }

  month++

  let totalDaysElapsed: number = DAYS_PER_YEAR
    * year
    + DAYS_PER_MONTH
    * month
    + day
    - DAYS_SINCE_NEW_MOON_1900_01_01

  totalDaysElapsed /= LUNAR_CYCLE // Divide by the lunar cycle.

  let phase: number = truncate(totalDaysElapsed)

  /*
    Subtract integer part to leave fractional part of original
    `totalDaysElapsed`.
   */
  totalDaysElapsed -= phase

  // Scale fraction from `0-8`.
  phase = round(totalDaysElapsed * 8)
  phase = phase & 7 // `0` and `8` are the same so turn `8` into `0`.

  if (phase >= EMoonPhase.COUNT || phase < EMoonPhase.New)
    throw new Error(`Invalid moon phase: ${phase}`)

  return { phase, name: MOON_PHASE_NAMES[phase] }

}

how can have contact with you?

sent you a repo collab

Yes, I think that wouldn't be too hard to add with some investigation into calculating lunar degrees.

how contact with you

You're cluttering up the gist man. I sent you a repo collaboration invite so you can contact me through the codebase.

You're cluttering up the gist man. I sent you a repo collaboration invite so you can contact me through the codebase.

i didnt have and received any thing

i accept it.now what?

This is my last message here. Check the README. My email is there.