Date.cc

/***********************************************************************************/
/*  Copyright 2009 WSL Institute for Snow and Avalanche Research    SLF-DAVOS      */
/***********************************************************************************/
/* This file is part of MeteoIO.
    MeteoIO is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    MeteoIO is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with MeteoIO.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <cmath>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <ctime>

#include <meteoio/dataClasses/Date.h>
#include <meteoio/IOUtils.h>
#include <meteoio/MathOptim.h>

using namespace std;

namespace mio {

#ifdef __MINGW32__
	//some version of MINGW have a buggy 64 bits implementation of difftime
	//this is Mingw bug 2152
	static __inline__
	double difftime( time_t __t1, time_t __t0 ) {
		if (sizeof(time_t)==8) { //time_t is 64 bits
			return (double)((long double)(__t1) - (long double)(__t0));
		} else {
			//return (double)((__int64)(__t1) - (__int64)(__t0));
			return (double)__t1 - (double)__t0;
		}
	}
#endif

const int Date::daysLeapYear[12] = {31,29,31,30,31,30,31,31,30,31,30,31};
const int Date::daysNonLeapYear[12] = {31,28,31,30,31,30,31,31,30,31,30,31};
const double Date::DST_shift = 1.0; //in hours
const float Date::MJD_offset = 2400000.5; ///<offset between julian date and modified julian date
const float Date::Unix_offset = 2440587.5; ///<offset between julian date and Unix Epoch time
const float Date::RFC868_offset = 2415020.5; ///< offset between julian date and RFC868 time (ref is 1900-01-01T00:00 GMT)
const float Date::Excel_offset = 2415018.5;  ///<offset between julian date and Excel dates (note that excel invented some days...)
const float Date::Matlab_offset = 1721058.5; ///<offset between julian date and Matlab dates

const double Date::epsilon=1./(24.*3600.025); ///< minimum difference between two dates. 1 second in units of days. 3600.025 is intentional
//NOTE: For the comparison operators, we assume that dates are positive so we can bypass a call to abs()

// CONSTUCTORS
/**
* @brief Default constructor: timezone is set to GMT without DST, julian date is set to 0 (meaning -4713-01-01T12:00)
*/
Date::Date() : timezone(0.), gmt_julian(0.),
               gmt_year(0), gmt_month(0), gmt_day(0), gmt_hour(0), gmt_minute(0), gmt_second(0),
               dst(false), undef(true)
{
}

/**
* @brief Julian date constructor.
* @param julian_in julian date to set
* @param in_timezone timezone as an offset to GMT (in hours, optional)
* @param in_dst is it DST? (default: no)
*/
Date::Date(const double& julian_in, const double& in_timezone, const bool& in_dst)
         : timezone(0.), gmt_julian(0.),
           gmt_year(0), gmt_month(0), gmt_day(0), gmt_hour(0), gmt_minute(0), gmt_second(0),
           dst(false), undef(true)
{
	setDate(julian_in, in_timezone, in_dst);
}

/**
* @brief Unix date constructor.
* @param in_time unix time (ie: as number of seconds since Unix Epoch, always UTC)
* @param in_dst is it DST? (default: no)
*/
Date::Date(const time_t& in_time, const bool& in_dst)
         : timezone(in_dst), gmt_julian(0.),
           gmt_year(0), gmt_month(0), gmt_day(0), gmt_hour(0), gmt_minute(0), gmt_second(0),
           dst(false), undef(true)
{
	setDate(in_time, in_dst);
}

/**
* @brief Date constructor by elements.
* All values are checked for plausibility.
* @param in_year in 4 digits
* @param in_month please keep in mind that first month of the year is 1 (ie: not 0!)
* @param in_day please keep in mind that first day of the month is 1 (ie: not 0!)
* @param in_hour
* @param in_minute
* @param in_timezone timezone as an offset to GMT (in hours, optional)
* @param in_dst is it DST? (default: no)
*/
Date::Date(const int& in_year, const int& in_month, const int& in_day, const int& in_hour, const int& in_minute, const double& in_timezone, const bool& in_dst)
         : timezone(in_timezone), gmt_julian(0.),
           gmt_year(0), gmt_month(0), gmt_day(0), gmt_hour(0), gmt_minute(0), gmt_second(0),
           dst(false), undef(true)
{
	setDate(in_year, in_month, in_day, in_hour, in_minute, in_timezone, in_dst);
}

// SETTERS
void Date::setUndef(const bool& flag) {
	undef = flag;
}

/**
* @brief Set internal gmt time from system time as well as system time zone.
*/
void Date::setFromSys() {
	const time_t curr = time(NULL);// current time in UTC
	tm local = *gmtime(&curr);// current time in UTC, stored as tm
	const time_t utc = mktime(&local);// convert GMT tm to GMT time_t
#ifndef __MINGW32__
	double tz = - difftime(utc,curr)/3600.; //time zone shift (sign so that if curr>utc, tz>0)
#else //workaround for Mingw bug 2152
	double tz = - mio::difftime(utc,curr)/3600.; //time zone shift (sign so that if curr>utc, tz>0)
#endif
	setDate( curr ); //Unix time_t setter, always in gmt
	setTimeZone( tz );
}

/**
* @brief Set timezone and Daylight Saving Time flag.
* @param in_timezone timezone as an offset to GMT (in hours)
* @param in_dst is it DST?
*/
void Date::setTimeZone(const double& in_timezone, const bool& in_dst) {
//please keep in mind that timezone might be fractional (ie: 15 minutes, etc)
	if(abs(in_timezone) > 12) {
		throw InvalidArgumentException("[E] Time zone can NOT be greater than +/-12!!", AT);
	}

	timezone = in_timezone;
	dst = in_dst;
}

/**
* @brief Copy setter.
* @param in_date Date object to copy
*/
void Date::setDate(const Date& in_date)
{
	if(in_date.isUndef()) {
		dst = false;
		undef = true;
	} else {
		setDate(in_date.getJulian(), in_date.getTimeZone(), in_date.getDST());
	}
}

/**
* @brief Set date by elements.
* All values are checked for plausibility.
* @param i_year in 4 digits
* @param i_month please keep in mind that first month of the year is 1 (ie: not 0!)
* @param i_day please keep in mind that first day of the month is 1 (ie: not 0!)
* @param i_hour
* @param i_minute
* @param i_second
* @param i_timezone timezone as an offset to GMT (in hours, optional)
* @param i_dst is it DST? (default: no)
*/
void Date::setDate(const int& i_year, const int& i_month, const int& i_day, const int& i_hour, const int& i_minute, const double& i_second, const double& i_timezone, const bool& i_dst)
{
	plausibilityCheck(i_year, i_month, i_day, i_hour, i_minute, i_second); //also checks leap years
	setTimeZone(i_timezone, i_dst);
	if(timezone==0 && dst==false) { //data is GMT and no DST
		//setting values and computing GMT julian date, rounded to internal precision of 1 second
		gmt_julian = rnd( calculateJulianDate(i_year, i_month, i_day, i_hour, i_minute, i_second), (unsigned)1);
	} else {
		//computing local julian date
		const double local_julian = calculateJulianDate(i_year, i_month, i_day, i_hour, i_minute, i_second);
		//converting local julian date to GMT julian date, rounded to internal precision of 1 second
		gmt_julian = rnd( localToGMT(local_julian), (unsigned)1);
	}
	//updating values to GMT, fixing potential 24:00 hour (ie: replaced by next day, 00:00)
	calculateValues(gmt_julian, gmt_year, gmt_month, gmt_day, gmt_hour, gmt_minute, gmt_second);
	undef = false;
}

void Date::setDate(const int& year, const unsigned int& month, const unsigned int& day, const unsigned int& hour, const unsigned int& minute, const double& second, const double& in_timezone, const bool& in_dst)
{
	setDate(year, (signed)month, (signed)day, (signed)hour, (signed)minute, second, in_timezone, in_dst);
}

/**
* @brief Set date by elements.
* All values are checked for plausibility.
* @param i_year in 4 digits
* @param i_month please keep in mind that first month of the year is 1 (ie: not 0!)
* @param i_day please keep in mind that first day of the month is 1 (ie: not 0!)
* @param i_hour
* @param i_minute
* @param i_second
* @param i_timezone timezone as an offset to GMT (in hours, optional)
* @param i_dst is it DST? (default: no)
*/
void Date::setDate(const int& i_year, const int& i_month, const int& i_day, const int& i_hour, const int& i_minute, const int& i_second, const double& i_timezone, const bool& i_dst)
{
	setDate(i_year, i_month, i_day, i_hour, i_minute, static_cast<double>(i_second), i_timezone, i_dst);
}

void Date::setDate(const int& year, const unsigned int& month, const unsigned int& day, const unsigned int& hour, const unsigned int& minute, const unsigned int& second, const double& in_timezone, const bool& in_dst)
{
	setDate(year, (signed)month, (signed)day, (signed)hour, (signed)minute, static_cast<double>(second), in_timezone, in_dst);
}

/**
* @brief Set date by elements.
* All values are checked for plausibility.
* @param i_year in 4 digits
* @param i_month please keep in mind that first month of the year is 1 (ie: not 0!)
* @param i_day please keep in mind that first day of the month is 1 (ie: not 0!)
* @param i_hour
* @param i_minute
* @param i_timezone timezone as an offset to GMT (in hours, optional)
* @param i_dst is it DST? (default: no)
*/
void Date::setDate(const int& i_year, const int& i_month, const int& i_day, const int& i_hour, const int& i_minute, const double& i_timezone, const bool& i_dst)
{
	setDate(i_year, i_month, i_day, i_hour, i_minute, 0., i_timezone, i_dst);
}

void Date::setDate(const int& year, const unsigned int& month, const unsigned int& day, const unsigned int& hour, const unsigned int& minute, const double& in_timezone, const bool& in_dst)
{
	setDate(year, (signed)month, (signed)day, (signed)hour, (signed)minute, 0., in_timezone, in_dst);
}

/**
* @brief Set date from a julian date (JD).
* @param julian_in julian date to set
* @param in_timezone timezone as an offset to GMT (in hours, optional)
* @param in_dst is it DST? (default: no)
*/
void Date::setDate(const double& julian_in, const double& in_timezone, const bool& in_dst) {
	setTimeZone(in_timezone, in_dst);
	gmt_julian = rnd( localToGMT(julian_in), (unsigned)1); //round to internal precision of 1 second
	calculateValues(gmt_julian, gmt_year, gmt_month, gmt_day, gmt_hour, gmt_minute, gmt_second);
	undef = false;
}

/**
* @brief Set date from a Unix date.
* @param i_time unix time (ie: as number of seconds since Unix Epoch, always UTC)
* @param i_dst is it DST? (default: no)
*/
void Date::setDate(const time_t& i_time, const bool& i_dst) {
	setUnixDate(i_time, i_dst);
}

/**
* @brief Set date from a modified julian date (MJD).
* @param julian_in julian date to set
* @param i_timezone timezone as an offset to GMT (in hours, optional)
* @param i_dst is it DST? (default: no)
*/
void Date::setModifiedJulianDate(const double& julian_in, const double& i_timezone, const bool& i_dst) {
	const double tmp_julian = julian_in + MJD_offset;
	setDate(tmp_julian, i_timezone, i_dst);
}

/**
* @brief Set date from an RFC868 date (time since 1900-01-01T00:00 GMT).
* @param julian_in julian date to set
* @param i_timezone timezone as an offset to GMT (in hours, optional)
* @param i_dst is it DST? (default: no)
*/
void Date::setRFC868Date(const double& julian_in, const double& i_timezone, const bool& i_dst) {
	const double tmp_julian = julian_in + RFC868_offset;
	setDate(tmp_julian, i_timezone, i_dst);
}

/**
* @brief Set date from a Unix date.
* @param in_time unix time (ie: as number of seconds since Unix Epoch, always UTC)
* @param in_dst is it DST? (default: no)
*/
void Date::setUnixDate(const time_t& in_time, const bool& in_dst) {
	const double in_julian = (double)(in_time)/(24.*60.*60.) + Unix_offset;
	setDate(in_julian, 0., in_dst);
}

/**
* @brief Set date from an Excel date.
* @param excel_in Excel date to set
* @param i_timezone timezone as an offset to GMT (in hours, optional)
* @param i_dst is it DST? (default: no)
*/
void Date::setExcelDate(const double excel_in, const double& i_timezone, const bool& i_dst) {
	//TODO: handle date < 1900-01-00 and date before 1900-03-01
	//see http://www.mathworks.com/help/toolbox/finance/x2mdate.html
	const double tmp_julian = excel_in + Excel_offset;
	setDate(tmp_julian, i_timezone, i_dst);
}

/**
* @brief Set date from an Matlab date.
* @param matlab_in Matlab date to set
* @param i_timezone timezone as an offset to GMT (in hours, optional)
* @param i_dst is it DST? (default: no)
*/
void Date::setMatlabDate(const double matlab_in, const double& i_timezone, const bool& i_dst) {
	const double tmp_julian = matlab_in + Matlab_offset;
	setDate(tmp_julian, i_timezone, i_dst);
}


// GETTERS
bool Date::isUndef() const {
	return undef;
}

/**
* @brief Returns timezone.
* @return timezone as an offset to GMT
*/
double Date::getTimeZone() const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	return timezone;
}

/**
* @brief Returns Daylight Saving Time flag.
* @return dst enabled?
*/
bool Date::getDST() const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	return dst;
}

/**
* @brief Return julian date (JD).
* The julian date is defined as the fractional number of days since -4713-01-01T12:00 UTC.
* @param gmt convert returned value to GMT? (default: false)
* @return julian date in the current timezone / in GMT depending on the gmt parameter
*/
double Date::getJulian(const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		return gmt_julian;
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		return local_julian;
	}
}

/**
* @brief Return modified julian date (MJD).
* The modified julian date is defined as the fractional number of days since 1858-11-17T00:00 UTC
* (definition by the Smithsonian Astrophysical Observatory, MA).
* @param gmt convert returned value to GMT? (default: false)
* @return modified julian date in the current timezone / in GMT depending on the gmt parameter
*/
double Date::getModifiedJulianDate(const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		return (gmt_julian - MJD_offset);
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		return (local_julian - MJD_offset);
	}
}

/**
* @brief Return RFC868 date.
* The RFC868 date is defined as the fractional number of days since 1900-01-01T00:00 GMT
* @param gmt convert returned value to GMT? (default: false)
* @return RFC868 julian date in the current timezone / in GMT depending on the gmt parameter
*/
double Date::getRFC868Date(const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		return (gmt_julian - RFC868_offset);
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		return (local_julian - RFC868_offset);
	}
}

/**
* @brief Return truncated julian date (TJD).
* The truncated julian date is defined as the julian day shifted to start at 00:00 and modulo 10000 days.
* The last origin (ie: 0) was 1995-10-10T00:00
* (definition by National Institute of Standards and Technology).
* @param gmt convert returned value to GMT? (default: false)
* @return truncated julian date in the current timezone / in GMT depending on the gmt parameter
*/
double Date::getTruncatedJulianDate(const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		return (fmod( (gmt_julian - 0.5), 10000. ));
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		return (fmod( (local_julian - 0.5), 10000. ));
	}
}

/**
* @brief Return Unix time (or POSIX time).
* The Unix time is defined as the number of seconds since 1970-01-01T00:00 UTC (Unix Epoch).
* It is therefore ALWAYS in GMT.
* (defined as IEEE P1003.1 POSIX. See http://www.mail-archive.com/leapsecs@rom.usno.navy.mil/msg00109.html
* for some technical, historical and funny insight into the standardization process)
* @return Unix time in the current timezone / in GMT depending on the gmt parameter
*/
time_t Date::getUnixDate() const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if (gmt_julian < Unix_offset)
		throw IOException("Dates before 1970 cannot be displayed in Unix epoch time", AT);

	return ( (time_t)floor( (gmt_julian - Unix_offset) * (24*60*60) ));
}

/**
* @brief Return Excel date.
* The (sick) Excel date is defined as the number of days since 1900-01-00T00:00 (no, this is NOT a typo).
* Moreover, it (wrongly) considers that 1900 was a leap year (in order to remain compatible with an old Lotus123 bug).
* This practically means that for dates after 1900-03-01, an Excel date really represents the number of days since 1900-01-01T00:00 PLUS 2.
* @param gmt convert returned value to GMT? (default: false)
* @return Excel date in the current timezone / in GMT depending on the gmt parameter
*/
double Date::getExcelDate(const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if (gmt_julian < Excel_offset)
		throw IOException("Dates before 1900 cannot be converted to Excel date", AT);

	if(gmt) {
		return ( gmt_julian - Excel_offset);
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		return ( local_julian - Excel_offset);
	}
}

/**
* @brief Return Matlab date.
* This is the number of days since 0000-01-01T00:00:00. See http://www.mathworks.com/help/techdoc/ref/datenum.html
* @param gmt convert returned value to GMT? (default: false)
* @return Matlab date in the current timezone / in GMT depending on the gmt parameter
*/
double Date::getMatlabDate(const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		return ( gmt_julian - Matlab_offset);
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		return ( local_julian - Matlab_offset);
	}
}


/**
* @brief Retrieve julian date.
* This method is a candidate for deletion: it should now be obsolete.
* @param julian_out julian date (in local time zone or GMT depending on the gmt flag)
* @param gmt convert returned value to GMT? (default: false)
*/
void Date::getDate(double& julian_out, const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		julian_out = gmt_julian;
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		julian_out = local_julian;
	}
}

/**
* @brief Return year.
* @param gmt convert returned value to GMT? (default: false)
* @return year
*/
int Date::getYear(const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		return gmt_year;
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		int local_year, local_month, local_day, local_hour, local_minute, local_second;
		calculateValues(local_julian, local_year, local_month, local_day, local_hour, local_minute, local_second);
		return local_year;
	}
}


/**
* @brief Return time of the day.
* @param hour_out
* @param minute_out
* @param gmt convert returned value to GMT? (default: false)
*/
void Date::getTime(int& hour_out, int& minute_out, const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		hour_out = gmt_hour;
		minute_out = gmt_minute;
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		int local_year, local_month, local_day, local_second;
		calculateValues(local_julian, local_year, local_month, local_day, hour_out, minute_out, local_second);
	}
}

/**
* @brief Return time of the day.
* @param hour_out
* @param minute_out
* @param second_out
* @param gmt convert returned value to GMT? (default: false)
*/
void Date::getTime(int& hour_out, int& minute_out, int& second_out, const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		hour_out = gmt_hour;
		minute_out = gmt_minute;
		second_out = gmt_second;
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		int local_year, local_month, local_day;
		calculateValues(local_julian, local_year, local_month, local_day, hour_out, minute_out, second_out);
	}
}

/**
* @brief Return year, month, day.
* @param year_out
* @param month_out
* @param day_out
* @param gmt convert returned value to GMT? (default: false)
*/
void Date::getDate(int& year_out, int& month_out, int& day_out, const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		year_out = gmt_year;
		month_out = gmt_month;
		day_out = gmt_day;
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		int local_hour, local_minute, local_second;
		calculateValues(local_julian, year_out, month_out, day_out, local_hour, local_minute, local_second);
	}
}

/**
* @brief Return year, month, day.
* @param year_out
* @param month_out
* @param day_out
* @param hour_out
* @param gmt convert returned value to GMT? (default: false)
*/
void Date::getDate(int& year_out, int& month_out, int& day_out, int& hour_out, const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		year_out = gmt_year;
		month_out = gmt_month;
		day_out = gmt_day;
		hour_out = gmt_hour;
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		int local_minute, local_second;
		calculateValues(local_julian, year_out, month_out, day_out, hour_out, local_minute, local_second);
	}
}

/**
* @brief Return year, month, day.
* @param year_out
* @param month_out
* @param day_out
* @param hour_out
* @param minute_out
* @param gmt convert returned value to GMT? (default: false)
*/
void Date::getDate(int& year_out, int& month_out, int& day_out, int& hour_out, int& minute_out, const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		year_out = gmt_year;
		month_out = gmt_month;
		day_out = gmt_day;
		hour_out = gmt_hour;
		minute_out = gmt_minute;
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		int local_second;
		calculateValues(local_julian, year_out, month_out, day_out, hour_out, minute_out, local_second);
	}
}

/**
* @brief Return year, month, day.
* @param year_out
* @param month_out
* @param day_out
* @param hour_out
* @param minute_out
* @param second_out
* @param gmt convert returned value to GMT? (default: false)
*/
void Date::getDate(int& year_out, int& month_out, int& day_out, int& hour_out, int& minute_out, int& second_out, const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		year_out = gmt_year;
		month_out = gmt_month;
		day_out = gmt_day;
		hour_out = gmt_hour;
		minute_out = gmt_minute;
		second_out = gmt_second;
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		calculateValues(local_julian, year_out, month_out, day_out, hour_out, minute_out, second_out);
	}
}

/**
* @brief Return the day of the week for the current date.
* The day of the week is between 1 (Monday) and 7 (Sunday).
* @param gmt convert returned value to GMT? (default: false)
*/
unsigned short Date::getDayOfWeek(const bool& gmt) const {
//principle: start from day julian=0 that is a Monday
	if (gmt) {
		const unsigned int dow = static_cast<unsigned int>(gmt_julian+.5) % 7 + 1;
		return static_cast<unsigned short>(dow);
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		const unsigned int dow = static_cast<unsigned int>(local_julian+.5) % 7 + 1;
		return static_cast<unsigned short>(dow);
	}
}

/**
* @brief Return the ISO 8601 week number
* The week number range from 1 to 53 for a leap year. The first week is the week that contains
* the first Thursday of the year. Previous days are attributed to the last week of the previous
* year (See https://en.wikipedia.org/wiki/ISO_week_date).
* @param gmt convert returned value to GMT? (default: false)
*/
unsigned short Date::getISOWeekNr(int &ISO_year, const bool& gmt) const
{
	ISO_year = getYear(gmt);
	const double jdn = getJulianDayNumber(gmt);
	Date newYear(*this - jdn + 1);
	const unsigned short newYear_dow = newYear.getDayOfWeek(gmt);
	const int firstThursday = (7 - newYear_dow + 4) % 7 + 1; //first Thursday of the year belongs to week 1
	const int firstWeekMonday = firstThursday - 3; //this could be <0, for example if Jan 01 is a Thursday
	
	if (jdn>=359) { //handle the last few days before the new year that might belong to week 1
		const bool is_leapYear = isLeapYear();
		const int jdn_last = (is_leapYear)? 366 : 365;
		const unsigned char week_offset = (is_leapYear)? 1 : 0; //for leap years, dec. 31 is one dow later as jan. 1st 
		const double lastDay_dow = (newYear_dow + week_offset - 1) % 7 + 1;
		const double lastMonday = jdn_last - lastDay_dow + 1; //dow starts at 1
		if (jdn>=lastMonday && lastDay_dow<4) {
			ISO_year++;
			return 1;
		}
	}
	
	//these are certainly normal days, ie no special case
	if (jdn>=firstWeekMonday) { //at worst, we are in week 01, otherwise after...
		return static_cast<unsigned short>( Optim::intPart( (jdn+3-(double)firstThursday) / 7 ) + 1);
	} else {
		//handle the first few days of the new year that are before week 1
		//we are *before* the Monday of the first week. This implies that dow>4 (otherwise, the current week would be week 01)
		//so these few days belong to the last week of the previous year
		ISO_year--;
		if (newYear_dow==5) return 53; // Friday indicates a leap year
		if (newYear_dow==7) return 52; // Sunday is no leap year
		
		//Saturday depends on the year before...
		if (isLeapYear(ISO_year)) return 53;
		else return 52;
	}
}

unsigned short Date::getISOWeekNr(const bool& gmt) const
{
	int ISO_year;
	return getISOWeekNr(ISO_year, gmt);
}

/**
* @brief Return the julian day for the current date.
* Return the day of the year index for the current Date object
* @param gmt convert returned value to GMT? (default: false)
* @return julian day number, starting from 1
*/
int Date::getJulianDayNumber(const bool& gmt) const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	if(gmt) {
		const double first_day_of_year = static_cast<double>(getJulianDayNumber(gmt_year, 1, 1));
		return static_cast<int>(gmt_julian - first_day_of_year + 1.5);
	} else {
		const double local_julian = GMTToLocal(gmt_julian);
		int local_year, local_month, local_day, local_hour, local_minute, local_second;
		calculateValues(local_julian, local_year, local_month, local_day, local_hour, local_minute, local_second);
		return static_cast<int>(Optim::intPart(local_julian+0.5)) - static_cast<int>(getJulianDayNumber(local_year, 1, 1)) + 1;
	}
}

/**
* @brief Return true if the current year is a leap year
* @return true if the current year is a leap year
*/
bool Date::isLeapYear() const {
	if(undef==true)
		throw UnknownValueException("Date object is undefined!", AT);

	return (isLeapYear( getYear() ));
}

/**
 * @brief Round a julian date to a given precision.
 * If you want to round a local date, do NOT provide it as gmt julian but as local julian,
 * otherwise things like rounding to the next day would be shifted by TimeZone.
 * @param julian date to round
 * @param precision round date to the given precision, in seconds
 * @param type rounding strategy (default: CLOSEST)
 */
double Date::rnd(const double& julian, const unsigned int& precision, const RND& type)
{
	if(precision == 0)
		throw InvalidArgumentException("Can not round dates to 0 seconds precision!", AT);

	double integral;
	const double fractional = modf(julian-.5, &integral);
	const double rnd_factor = (3600*24)/(double)precision;

	if(type==CLOSEST)
		return integral + (double)Optim::round( fractional*rnd_factor ) / rnd_factor + .5;
	if(type==UP)
		return integral + (double)Optim::ceil( fractional*rnd_factor ) / rnd_factor + .5;
	if(type==DOWN)
		return integral + (double)Optim::floor( fractional*rnd_factor ) / rnd_factor + .5;

	throw UnknownValueException("Unknown rounding strategy!", AT);
}

/**
 * @brief Round date to a given precision
 * @param precision round date to the given precision, in seconds
 * @param type rounding strategy (default: CLOSEST)
 */
void Date::rnd(const unsigned int& precision, const RND& type) {
	if(!undef) {
		const double rnd_julian = rnd( getJulian(false), precision, type ); //round local time
		setDate(rnd_julian, timezone, dst);
	}
}

const Date Date::rnd(const Date& indate, const unsigned int& precision, const RND& type) {
	Date tmp(indate);
	if(!tmp.undef) {
		const double rnd_julian = rnd( tmp.getJulian(false), precision, type ); //round local time
		tmp.setDate(rnd_julian, tmp.getTimeZone(), tmp.getDST());
	}

	return tmp;
}

// OPERATORS //HACK this will have to handle Durations
Date& Date::operator+=(const Date& indate) {
	if(undef==true || indate.isUndef()) {
		undef=true;
		return *this;
	}
	gmt_julian += indate.gmt_julian;
	rnd(1); //round to internal precision of 1 second
	calculateValues(gmt_julian, gmt_year, gmt_month, gmt_day, gmt_hour, gmt_minute, gmt_second);
	return *this;
}

Date& Date::operator-=(const Date& indate) {
	if(undef==true || indate.isUndef()) {
		undef=true;
		return *this;
	}
	gmt_julian -= indate.gmt_julian;
	rnd(1); //round to internal precision of 1 second
	calculateValues(gmt_julian, gmt_year, gmt_month, gmt_day, gmt_hour, gmt_minute, gmt_second);
	return *this;
}

Date& Date::operator+=(const double& indate) {
	if(undef==false) {
		gmt_julian += indate;
		rnd(1); //round to internal precision of 1 second
		calculateValues(gmt_julian, gmt_year, gmt_month, gmt_day, gmt_hour, gmt_minute, gmt_second);
	}
	return *this;
}

Date& Date::operator-=(const double& indate) {
	if(undef==false) {
		gmt_julian -= indate;
		rnd(1); //round to internal precision of 1 second
		calculateValues(gmt_julian, gmt_year, gmt_month, gmt_day, gmt_hour, gmt_minute, gmt_second);
	}
	return *this;
}

Date& Date::operator*=(const double& value) {
	if(undef==false) {
		gmt_julian *= value;
		rnd(1); //round to internal precision of 1 second
		calculateValues(gmt_julian, gmt_year, gmt_month, gmt_day, gmt_hour, gmt_minute, gmt_second);
	}
	return *this;
}

Date& Date::operator/=(const double& value) {
	if(undef==false) {
		gmt_julian /= value;
		rnd(1); //round to internal precision of 1 second
		calculateValues(gmt_julian, gmt_year, gmt_month, gmt_day, gmt_hour, gmt_minute, gmt_second);
	}
	return *this;
}

bool Date::operator==(const Date& indate) const {
	if(undef==true || indate.isUndef()) {
		return( undef==true && indate.isUndef() );
	}

	return IOUtils::checkEpsilonEquality(gmt_julian, indate.gmt_julian, epsilon);
}

bool Date::operator!=(const Date& indate) const {
	return !(*this==indate);
}

bool Date::operator<(const Date& indate) const {
	if(undef==true || indate.isUndef()) {
		throw UnknownValueException("Date object is undefined!", AT);
	}

#ifdef NEGATIVE_JULIAN
	if(*this==indate) return false;
	return (gmt_julian < indate.gmt_julian);
#else
	return (gmt_julian < (indate.gmt_julian-epsilon));
#endif
}

bool Date::operator<=(const Date& indate) const {
	if(undef==true || indate.isUndef()) {
		throw UnknownValueException("Date object is undefined!", AT);
	}

#ifdef NEGATIVE_JULIAN
	if(*this==indate) return true;
	return (gmt_julian <= indate.gmt_julian);
#else
	return (gmt_julian <= (indate.gmt_julian+epsilon));
#endif
}

bool Date::operator>(const Date& indate) const {
	if(undef==true || indate.isUndef()) {
		throw UnknownValueException("Date object is undefined!", AT);
	}

#ifdef NEGATIVE_JULIAN
	if(*this==indate) return false;
	return (gmt_julian > indate.gmt_julian);
#else
	return (gmt_julian > (indate.gmt_julian+epsilon));
#endif
}

bool Date::operator>=(const Date& indate) const {
	if(undef==true || indate.isUndef()) {
		throw UnknownValueException("Date object is undefined!", AT);
	}

#ifdef NEGATIVE_JULIAN
	if(*this==indate) return true;
	return (gmt_julian >= indate.gmt_julian);
#else
	return (gmt_julian >= (indate.gmt_julian-epsilon));
#endif
}

const Date Date::operator+(const Date& indate) const {
	if(undef==true || indate.isUndef()) {
		Date tmp; //create an Undef date
		return tmp;
	}

	Date tmp(gmt_julian + indate.gmt_julian, 0.);
	tmp.setTimeZone(timezone);
	return tmp;
}

const Date Date::operator-(const Date& indate) const {
	if(undef==true || indate.isUndef()) {
		Date tmp; //create an Undef date
		return tmp;
	}

	Date tmp(gmt_julian - indate.gmt_julian, 0.);
	tmp.setTimeZone(timezone);
	return tmp;
}

const Date Date::operator+(const double& indate) const {
	//remains undef if undef
	Date tmp(gmt_julian + indate, 0.);
	tmp.setTimeZone(timezone);
	return tmp;
}

const Date Date::operator-(const double& indate) const {
	//remains undef if undef
	Date tmp(gmt_julian - indate, 0.);
	tmp.setTimeZone(timezone);
	return tmp;
}

const Date Date::operator*(const double& value) const {
	//remains undef if undef
	Date tmp(gmt_julian * value, 0.);
	tmp.setTimeZone(timezone);
	return tmp;
}

const Date Date::operator/(const double& value) const {
	//remains undef if undef
	Date tmp(gmt_julian / value, 0.);
	tmp.setTimeZone(timezone);
	return tmp;
}

/**
* @brief Parse an ISO 8601 formatted time zone specification.
* Time zones MUST be specified right after a date/time/combined representation
* according to the following formats:
*   - 'Z' like in 2013-02-13T19:43Z, meaning GMT
*   - '+01' like in 2013-02-13T20:43+01 meaning GMT+1
*   - '+0130' like in 2013-02-13T21:13+0130 meaning GMT+1.5
*   - '+01:30' like in 2013-02-13T21:13+01:30 meaning GMT+1.5
*   - '-0515' like in 2013-02-13T15:28-0515 meaning GMT-5.25
* See https://en.wikipedia.org/wiki/ISO_8601 for more information
* @param timezone_iso time zone string
* @return time zone/shift in hours
*/
double Date::parseTimeZone(const std::string& timezone_iso)
{
	if(timezone_iso.empty()) //just in case, to avoid a segfault