imported>Verdy p at 17:26, 20 April 2013

2013-04-20T17:26:19Z

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local Error = require('Module:Error');

local this = {};

function this.julianDayOfDate(date)
-- http://www.tondering.dk/claus/cal/julperiod.php#formula
local y = date.year + 4799; -- Set epoch in 1 March -4800, but counting months from January as the 10th month of previous year.
local m = y * 12 + date.month + 9; -- Total number of months since epoch (January = 10, December = 21).
y = math.floor(m / 12); m = m - y * 12; -- Split total months into relative months...
return
math.floor(y * 1461 / 4) -- Julian cycle of 1461 days every 4 years.
+ math.floor((m + 4) * 153 / 5) -- Days in relative month (need to substract 122 at end).
+ date.day -- Additional days (need to substract 1 at end).
+ (date.hour - 12) / 24 -- The time part.
+ date.minute / 1440
+ date.second / 86400 -- (leap seconds ignored, every day assumed to be 86400 seconds exactly).
- 32204; -- Final substractive constant 32204 == 32081 + 122 + 1.
end;

function this.dateOfJulianDay(JD)
-- Check parameters.
if JD == nil then
return Error.error{"Parameter 1=''Julian day'' is either missing or has wrong format!"};
end;

local date = {};
date.weekday = JD + 0.5 - math.floor((JD + 0.5) / 7) * 7; -- 0 = Monday, 6 = Sunday.

-- See [[fr:Formules de calcul du calendrier grégorien]] on Wikipedia for explained details and intermediate values in test cases.
JD = JD + 32081.5;
local j = math.floor(JD); -- no rounding performed for the precision of time; if you need it, round the JD before calling this method.

-- 1461 days per cycle of 4 years (no adjustment needed).
local b = math.floor(dc / 1461);
local db = dc - b * 1461;

-- 365 days per cycle of 1 year (cycle numbers: 0 to 4; but 4 is reduced to 3, making sometimes the last cycle longer longer by 1 day).
-- Note: for a in 0..4: math.min(a, 3) is equal to math.floor((a * 3 + 1) / 4); this avoids conditional branches:
-- 0 -> 0 = floor(1 / 4); 1 -> 1 = floor(4 / 4); 2 -> 2 = floor(7 / 4); 3 -> 3 = floor(10 / 4); 4 -> 4 = floor(13 / 4)
local a = math.floor((math.floor(db / 365) * 3 + 1) / 4);
local da = db - a * 365;

-- Relative date since epoch (1 March -4800).
local y = b * 4 + a;
local m = math.floor((da * 5 + 308) / 153) - 2;
local d = da - math.floor((m + 4) * 153 / 5) + 122;

-- Actual Julian date.
date.year = y - 4800 + math.floor((m + 2) / 12);
date.month = m - math.floor((m + 2) / 12) * 12 + 3;
date.day = d + 1;--//Test:1

-- Actual time of day (leap seconds ignored, every day assumed to be 86400 seconds exactly).
j = (JD + 0.5 - math.floor(JD + 0.5)) * 24;
date.hour = math.floor(j);
j = (j - date.hour) * 60;
date.minute = math.floor(j);
date.second = (j - date.minute) * 60; -- No rounding performed; this includes fractions of seconds.
return date;
end;

function this.julianDay(year, month, day, hour, minute, second)
-- Check parameters and set defaults.
if year == nil then
return Error.error{"Parameter 1=''year'' is either missing or has wrong format!"};
end;
if month == nil then month = 1; end;
if day == nil then day = 1; end;
if hour == nil then hour = 12; end;
if minute == nil then minute = 0; end;
if second == nil then second = 0; end;
return this.julianDayOfDate({year = year, month = month, day = day, hour = hour, minute = minute, second = second});
end;

-- Basic formatting (for debugging only ?).
function this.wikiDateOfJulianDay(JD)
-- Check parameters.
if JD == nil then
return Error.error{"Parameter 1=''Julian day'' is either missing or has wrong format!"};
end;

local date = this.dateOfJulianDay(JD);
return tostring(date.year)
.. "|" .. tostring(date.month)
.. "|" .. tostring(date.day)
.. "|" .. tostring(date.hour)
.. "|" .. tostring(date.minute)
.. "|" .. tostring(date.second);
end;

-- English formatting (for display or tests ? not internationalized).
function this.EnglishDateOfJulianDay(JD)
-- Check parameters.
if JD == nil then
return Error.error{"Parameter 1=''Julian day'' is either missing or has wrong format!"};
end;

local date = this:dateOfJulianDay(JD);

local s = "";
if (date >= 0 and date.day < 10) then
s = s .. "0" .. tostring(date.day);
else
s = s .. tostring(date.day);
end
local months = {
"January", "February", "March", "April", "May", "June",
"July", "August", "September", "October", "November", "December"
};
s = s .. " " .. months[date.month - 1] .. " ";
if (date.year < 0) then
s = s .. tostring(1 - date.year) .. " BC ";
else
s = s .. tostring(date.year) .. " AD ";
end
if (date.hour >= 0 and date.hour < 10) then
s = s .. "0" .. tostring(date.hour) .. ":";
else
s = s .. tostring(date.hour) .. ":";
end
if (date.minute >= 0 and date.minute < 10) then
s = s .. "0" .. tostring(date.minute) .. ":";
else
s = s .. tostring(date.minute) .. ":";
end
if (date.second >= 0 and date.second < 10) then
s = s .. "0" .. tostring(date.second);
else
s = s .. tostring(date.second);
end
return s .. " UTC";
end;

function this.yearOfJulianDay(JD)
-- Check parameters.
if JD == nil then
return Error.error{"Parameter 1=''Julian day'' is either missing or has wrong format!"};
end;

return this.dateOfJulianDay(JD).year;
end;

function this.monthOfJulianDay(JD)
-- Check parameters.
if JD == nil then
return Error.error{"Parameter 1=''Julian day'' is either missing or has wrong format!"};
end;

return this.dateOfJulianDay(JD).month;
end;

function this.dayOfJulianDay(JD)
-- Check parameters.
if JD == nil then
return Error.error{"Parameter 1=''Julian day'' is either missing or has wrong format!"};
end;

return this.dateOfJulianDay(JD).day;
end;

function this.weekdayOfJulianDay(JD)
-- Check parameters.
if JD == nil then
return Error.error{"Parameter 1=''Julian day'' is either missing or has wrong format!"};
end;

return this.dateOfJulianDay(JD).weekday;
end;

function this.hourOfJulianDay(JD)
-- Check parameters.
if JD == nil then
return Error.error{"Parameter 1=''Julian day'' is either missing or has wrong format!"};
end;

return this.dateOfJulianDay(JD).hour;
end;

function this.minuteOfJulianDay(JD)
-- Check parameters.
if JD == nil then
return Error.error{"Parameter 1=''Julian day'' is either missing or has wrong format!"};
end;

return this.dateOfJulianDay(JD).minute;
end;

function this.secondOfJulianDay(JD)
-- Check parameters.
if JD == nil then
return Error.error{"Parameter 1=''Julian day'' is either missing or has wrong format!"};
end;

return this.dateOfJulianDay(JD).second;
end;

return this;

Module:Sandbox/DixonD/Datetime/Julian - Revision history

imported>Verdy p at 17:26, 20 April 2013