N6LDate

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N6LDate: High-Precision Calendar Calculation Class

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N6LDate is a high-precision, feature-rich calendar calculation class that extends the standard JavaScript Date object. Key features include:

• Support for calendar changes (Gregorian/Julian) specific to different countries
• Mutual conversion between JD (Julian Day) and MJD
• Mutual conversion with UNIX time (seconds / milliseconds)
• Support for region-specific day-of-week and month names
• Polymorphic constructor (supports 7+ input formats)
• Calendar normalization via normalize()
• Precision suitable for orbital calculations and astronomical applications

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Class Overview

const dt = new N6LDate().normalize();

N6LDate uses a two-stage initialization model:

1. constructor Sets values ??only (does not guarantee calendar consistency)
2. normalize() Handles calendar changes, month-length adjustments, day-of-week calculations, UNIX recalculation, etc.

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Constructor Specifications

Supported Input Formats

Input Format	Example	Description
No arguments	new N6LDate()	Current time (Date-compatible)
N6LDate instance	new N6LDate(dt)	Exact copy
Date object	new N6LDate(new Date())	Convert from Date
String	new N6LDate("2030-09-15T12:00:00Z")	Date.parse() compatible
UNIX milliseconds	new N6LDate(Date.now())	UNIX ms → JD → Calendar
Year, Month, Day	new N6LDate(2030,9,15)	Set calendar values ??directly
Y, M, D, h, m, s, ms	new N6LDate(2030,9,15,12,34,56,789)	Fractional values ??adjusted via normalize()

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normalize()

An essential process to ensure calendar consistency.

• Month length adjustment
• Year length adjustment
• Calendar reform (ReformTable) application
• Day-of-week calculation
• UNIX time recalculation
• JD / MJD recalculation

const dt = new N6LDate(2030,9,15,12).normalize();

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Regional Settings (Days of the Week / Month Names)

N6LDate switches the names of days of the week and months based on the region code.

Example:

dt.regionW = "JP"; // Japanese day names
dt.region  = "JP"; // Japanese calendar reform

Supported regions: JP / EN / FR / DE / ES / IT / PT / RU / GR / … (many others)

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Calendar Reform (ReformTable)

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Stores the transition dates from the Julian calendar to the Gregorian calendar, which vary by country.

Example (Japan):

1582-10-04 → 1582-10-15 (10-day gap)

Automatically applied during normalize(). ---

JD / MJD

toJD()

const jd = dt.toJD();

fromJD()

dt.fromJD(jd).normalize();

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UNIX Time (Seconds / Milliseconds)

Seconds Version (Standard)

toUNIX()      // UNIX seconds
fromUNIX(sec) // UNIX seconds → Calendar date

Milliseconds Version (Compatible with Date.getTime())

toUNIXms()      // UNIX milliseconds
fromUNIXms(ms)  // UNIX milliseconds → Calendar date

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Formatted Output (toString)

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Format Constants

static get N6LDATE_FMT_DEFAULT()  { return 0; }  // Local format (Date + Day of Week + Time)
static get N6LDATE_FMT_FULL()     { return 1; }  // Local format (Date + Time + Day of Week)
static get N6LDATE_FMT_NW()       { return 2; }  // Local format (Date + Time, no Day of Week)

static get N6LDATE_FMT_DATE()     { return 3; }  // Local format (Date + Day of Week)
static get N6LDATE_FMT_DATE_NW()  { return 4; }  // Local format (Date, no Day of Week)

static get N6LDATE_FMT_ISO()      { return 5; }  // ISO format (YYYY-MM-DD(Day) T hh:mm:ss.SSS Z)
static get N6LDATE_FMT_ISO_W()    { return 6; }  // ISO format (YYYY-MM-DD T hh:mm:ss.SSS Z + Day of Week)
static get N6LDATE_FMT_ISO_NW()   { return 7; }  // ISO format (YYYY-MM-DD T hh:mm:ss.SSS Z)

static get N6LDATE_FMT_ISO_D()    { return
``` 8; }  // ISO format (YYYY-MM-DD + day of week)
static get N6LDATE_FMT_ISO_D_NW() { return 9; }  // ISO format (YYYY-MM-DD)

Usage Example

dt.toString(N6LDate.N6LDATE_FMT_ISO);

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Custom Format (format)

Format Specifiers

var pad = (n, len = 2) => String(n).padStart(len, '0');

const map = {
"YYYY": year,
"YY": String(year).slice(-2),
"MMMM": monthName,
"MMM": monthName.slice(0,3),
"MM": pad(month),
"M": month,
"DD": pad(day),
"D": day,
"hh": pad(hour),
"h": hour,
"HH": pad(hour),
"mm": pad(minute),
"m": minute,
"ss": pad(second),
"s": second,
"SSS": pad(ms,3),
"A": ampm,
"W": weekStr
};

Usage Example

dt.format("YYYY-MM-DD hh:mm:ss.SSS (W)")

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Usage Examples (Summary)

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const dt = new N6LDate(2030,9,15,12).normalize();
const target = new N6LDate(2060,9,15,12).normalize();

console.log(dt.toString());                        // Local format
console.log(dt.toUNIX());                          // UNIX seconds
console.log(dt.toUNIXms());                        // UNIX milliseconds
console.log(dt.toJD());                            // JD
console.log(dt.toString(N6LDate.N6LDATE_FMT_ISO)); // ISO format
console.log(dt.adjustCalendar(1).toString());      // Adjust by adding 1 day
console.log(dt.addDays(-1.25).toString());         // Add -1.25 days
console.log(dt.diffDays(target));                  // Difference in days

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List of Member Functions

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//Programmed by NAS6
//date.js

class N6LDate {

//Always append .normalize(), e.g., var dt = new N6LDate().normalize();
constructor(ya, ma, da, ho, mo, so, ms, region = "DEFAULT", regionW = "DEFAULT")
//Clone
clone()
tempPDays(val)
adjustTime(val)

//Get total days (automatic handling of Julian/Gregorian calendars; includes potential errors)
//For accurate elapsed days, retrieve N6LDate.pastday or N6LDate.ms after calling normalize() or adjustCalendar()
calendarToDay(val, flg = false)

//Convert to previous day
suboneday(val)
//Parse date
parseDate(str)

//Get week
getWeek()
//Get total milliseconds / tick time (Epoch: 1/1/1 0:0:0.000)
getMS()
//Get total days (Epoch: 1/1/1 0:0:0.000)
getPDays()
//Get time
getTime()
//Week number
getWeekNumber()

//ISO Week Date (ISO 8601)
getISOWeekDate()
//ISO 8601 Time Duration (duration notation)
getISOTimeDuration(target)
// Calendar reform information
getReformInfo(region = "GB", lng = "DEFAULT")

// Julian/Gregorian calendar reform
afterGregorian(val)
// Check if the current year is a leap year
isLeap(val, flg = true)
// Check if it is the end of the month
isMonthEnd(val)
// Get the end of the month
getMonthEnd(val, flg = true)
// Period count up collection(y,ry,term) // Get cumulative leap years
getLeap(val)

// Includes modification of 'this'
SetVal(val)

// Generate a Gregorian date object from a cumulative day count
gregorianDayToDate(targetDay, flg = true)
// Julian calendar addition (generate a Julian date object from a cumulative day count)
julianDayToDate(targetDay, flg = false)
// Date adjustment (automatic handling for Julian/Gregorian calendars)
adjustCalendar(rh = null)
// [!!!Cumulative milliseconds!!!][Date/Time/Week] Normalization
// Includes modification of 'this'
// Normalize the object's date and time (safe implementation avoiding recursion)
normalize()

// Get difference in milliseconds (this - target)
diffMS(target)
// Get difference in days (this - target)
diffDays(target)
// Get difference structure (this - target)
diffDuration(target)

// Comparison operations
isBefore(target)
isAfter(target)
isEqual(target, eps = 1e-6)

// N6LDate standard format constants
// Used as preset specifiers for toString(fmtsw)
static get N6LDATE_FMT_DEFAULT() { return 0; } // "2026/07/29(Wed) 04:55:04.123"
static get N6LDATE_FMT_FULL() { return 1; } // "2026/07/29 04:55:04.123 (Wed)"
static static get N6LDATE_FMT_NW() { return 2; } // "2026/07/29 04:55:04.123"
static get N6LDATE_FMT_DATE() { return 3; } // "2026/07/29(Wed)"
static get N6LDATE_FMT_DATE_NW() { return 4; } // "2026/07/29"
static get N6LDATE_FMT_ISO() { return 5; } // "2026-07-29(Wed) T 04:55:04.123 Z"
static get N6LDATE_FMT_ISO_W() { return 6; } // "2026-07-29 T 04:55:04.123 Z (Wed)"
static get N6LDATE_FMT_ISO_NW() { return 7; } // "2026-07-29 T 04:55:04.123 Z"
static get N6LDATE_FMT_ISO_D() { return 8; } // "2026-07-29(Wed)"
static get N6LDATE_FMT_ISO_D_NW() { return 9; } // "2026-07-29"

// Formatted output (e.g., "2026/07/29 04:55:04 Wed")
toString(fmtsw = 0)
// Custom format output
// e.g., date.format("YYYY-MM-DD hh:mm:ss.SSS (W)")
format(pattern)

// Date object output
toDate()
// Temporal object output
toTemporal()
// Create with current date and time
Now()

// Julian Day
toJD()
fromJD(rh)
// Modified Julian Day
toMJD()
fromMJD(rh)
// Unix time (seconds)
toUNIX()
fromUNIX(rh)
// Unix time (milliseconds)
toUNIXms()
fromUNIXms(rh)

// Serialization
//const dt = new N6LDate(2030, 9, 15, 12, 34, 56, 789).normalize();
//dt.region = "JP";
//const json = JSON.stringify(dt); // toJSON is called automatically
// → {"year":2030,"month":9,"day":15,...}
//const restored = N6LDate.fromJSON(JSON.parse(json));
//console.log(restored.toString()); // 2030/09/15(Sun) 12:34:56.789
toJSON()
static fromJSON(json)
startOf(unit)
endOf(unit)

// Various addition methods // Simply calls adjustCalendar with the argument treated as elapsed days (including fractions)
addYears(rh)
addMonths(rh)
addDays(rh)
addHours(rh)
addMinutes(rh)
addSeconds(rh)
addMSs(rh)
}

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License

License: GPL-3.0

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