Julian Day Conversion Utility Functions

JulianDayUtilities.swift

import Foundation

func jdFromDate(date : NSDate) -> Double {
    let JD_JAN_1_1970_0000GMT = 2440587.5
    return JD_JAN_1_1970_0000GMT + date.timeIntervalSince1970 / 86400
}

func dateFromJd(jd : Double) -> NSDate {
    let JD_JAN_1_1970_0000GMT = 2440587.5
    return  NSDate(timeIntervalSince1970: (jd - JD_JAN_1_1970_0000GMT) * 86400)
}

func date(year: Int, month: Int, day: Int) -> NSDate {
    let comps = NSDateComponents()
    comps.year = year
    comps.month = month
    comps.day = day
    comps.hour = 12
    let gregorian = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)
    let date = gregorian?.dateFromComponents(comps)
    return date!
}

func dateFromISO8601(string:String) -> NSDate {
    var array = string.componentsSeparatedByString("-")
    array = array.reverse()
    var year = 1970, month = 1, day = 1
    if array.count >= 3 {
        year = Int(array[2]) ?? year
    }
    if array.count >= 2 {
        month = Int(array[1]) ?? year
    }
    if array.count >= 1 {
        day = Int(array[0]) ?? year
    }
    return date(year, month: month, day: day)
}

func dateByJapaneseCalendar(era: Int, year: Int, month:Int, day:Int ) -> NSDate {
    let comps = NSDateComponents()
    comps.era = era
    comps.year = year
    comps.month = month
    comps.day = day
    comps.hour = 12
    let calendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierJapanese)
    let date = calendar?.dateFromComponents(comps)
    return date!
}

func dateByChineseCalendar(year: Int, month:Int, day:Int ) -> NSDate {
    let comps = NSDateComponents()
    comps.year = year
    comps.month = month
    comps.day = day
    let calendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierRepublicOfChina)
    let date = calendar?.dateFromComponents(comps)
    return date!
}

func jdFromMjd(mjd:Double) -> Double {
    let MJD_BASE_18581117 = 2400000.5
    return mjd + MJD_BASE_18581117
}

func mjdFromJd(jd:Double) -> Double {
    let MJD_BASE_18581117 = 2400000.5
    return jd - MJD_BASE_18581117
}

func ldFromJd(jd:Double) -> Int {
    let LILIAN_DAY_BASE = 2_299_159.5
    return Int(jd - LILIAN_DAY_BASE)
}

func jdFromLd(ld:Int) -> Double {
    let LILIAN_DAY_BASE = 2_299_159.5
    return Double(ld) + LILIAN_DAY_BASE
}

func jdFromGregorianDate(date:NSDate) -> Double {
    let calendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)
    let flags = NSCalendarUnit([.Year,.Month,.Day])
    guard let comps = calendar?.components(flags, fromDate: date) else {
        return 2440587.5
    }
    let year = comps.year, month = comps.month, day = comps.day
    let y = year + (month - 3)/12
    let m = (month - 3) % 12
    let d = day - 1
    let n = d + (153 * m + 2) / 5 + 365 * y + y / 4 - y / 100 + y / 400
    let mjd = n - 678881
    let jd = Double(mjd) + 2400000.5
    return jd
}

func gregorianDateFromJd(jd:Double) -> NSDate {
    let mjd = jd - 2400000.5
    let n = Int(mjd) + 678881
    let a = 4 * n + 3 + 4 * ( ( ( 4 * ( n + 1 ) / 146097 ) + 1 ) * 3 / 4 )
    let b = 5 * ( ( a % 1461 ) / 4 ) + 2
    let y = a / 1461
    let m = b / 153
    let d = ( b % 153 ) / 5
    
    let day = d + 1
    let month = ( m + 3 ) % 12
    let year = y - m / 12
    return date(year, month: month, day: day)
}

func jdFromJulianDate(year: Int, month: Int, day: Int ) -> Double {
    let y = year + (month - 3)/12
    let m = (month - 3) % 12
    let d = day - 1
    let n = d + (153 * m + 2) / 5 + 365 * y + y / 4
    let mjd = n - 678883
    let jd = Double(mjd) + 2400000.5
    return jd
}

func julianDateFromJd(jd:Double) -> NSDateComponents {
    let mjd = jd - 2400000.5
    let n = Int(mjd) + 678883
    let a = 4 * n + 3
    let b = 5 * ( ( a % 1461 ) / 4 ) + 2
    let y = a / 1461
    let m = b / 153
    let d = ( b % 153 ) / 5
    
    let day = d + 1
    let month = ( m + 3 ) % 12
    let year = y - m / 12
    
    let comps = NSDateComponents()
    comps.year = year
    comps.month = month
    comps.day = day
    return comps
}

// 0 = Wednesday, 1 = Thursday, 2 = Friday, 3 = Saturday,
// 4 = Sunday, 5 = Monday, 6 = Tuesday
func weekdayFromMjd_Wednesday0(mjd:Double) -> Int {
    return Int(mjd) % 7
}

// 1 = Sunday, 2 = Monday, 3 = Tuesday
// 4 = Wednesday, 5 = Thursday, 6 = Friday, 7 = Saturday,
func weekdayFromMjd(mjd:Double) -> Int {
    let weekday = weekdayFromMjd_Wednesday0(mjd)
    return ( weekday + 3 ) % 7 + 1
}
func weekdayFromJd(jd:Double) -> Int {
    let mjd = mjdFromJd(jd)
    return weekdayFromMjd(mjd)
}
enum Weekday : Int {
    case Sunday = 1
    case Monday
    case Tuesday
    case Wednesday
    case Thursday
    case Friday
    case Saturday
}

// 余り	0	1	2	3	4	5	6	7	8	9	10	11
// 十二支	寅	卯	辰	巳	午	未	申	酉	戌	亥	子	丑
func juunisiFromMjd_Tora0(mjd:Double) -> Int {
    return Int(mjd) % 12
}
// 余り	0	1	2	3	4	5	6	7	8	9	10	11
// 十二支	子	丑	寅	卯	辰	巳	午	未	申	酉	戌	亥
func juunisiFromMjd(mjd:Double) -> Int {
    return ( juunisiFromMjd_Tora0(mjd) + 2 ) % 12
}
enum Juunisi : Int {
    case Ne = 0
    case Usi
    case Tora
    case U
    case Tatu
    case Mi
    case Uma
    case Hituji
    case Saru
    case Tori
    case Inu
    case I
}

// 余り	0	1	2	3	4	5	6	7	8	9
// 十干	甲	乙	丙	丁	戊	己	庚	辛	壬	癸
func jikanFromMjd(mjd:Double) -> Int {
    return Int(mjd) % 10
}
func jikanFromJd(jd:Double) -> Int {
    return jikanFromMjd(mjdFromJd(jd))
}
enum Jikan : Int {
    case Kinoe = 1
    case Kinoto
    case Hinoe
    case Hinoto
    case Tutinoe
    case Tutinoto
    case Kanoe
    case Kanoto
    case Mizunoe
    case Mizunoto
}

// 0 = 甲寅
func kansiFromMjd_KinoeTora0(mjd:Double) -> Int {
    return Int(mjd) % 60
}
// 0 = 甲子
func kansiFromMjd(mjd:Double) -> Int {
    return ( kansiFromMjd_KinoeTora0(mjd) + 50 ) % 60
}
func kansiFromJd(jd:Double) -> Int {
    return kansiFromMjd(mjdFromJd(jd))
}