perturb::JulianDate Struct Reference

Represents a specific point in time on the Julian calendar. More...

#include <perturb.hpp>

Public Member Functions
	JulianDate ()
	Construct an empty julian date initialized to 0.
	JulianDate (double jd)
	Construct from a Julian number of days since epoch (4713 B.C.)
	JulianDate (double jd, double jd_frac)
	Construct from a Julian day number and fractional day. More...
	JulianDate (DateTime t)
	Construct from a DateTime time point. More...
DateTime	to_datetime () const
	Convert to a DateTime representing the same time point. More...
void	normalize ()
	Normalizes a Julian date representation to a canonical representation. More...
JulianDate	normalized () const
	Get a normalized copy of a julian date.
double	operator- (const JulianDate &rhs) const
	Returns the difference/delta in times as a fractional number of days.
JulianDate	operator+ (const double &delta_jd) const
	Returns another time point offset by a number of days. More...
JulianDate &	operator+= (const double &delta_jd)
	Add a delta number of days offset to this time point.
JulianDate	operator- (const double &delta_jd) const
	Returns another time point offset backwards by a number of days.
JulianDate &	operator-= (const double &delta_jd)
	Subtracts a delta number of days offset to this time point.
bool	operator< (const JulianDate &rhs) const
	Compare if chronologically earlier than another time point.
bool	operator> (const JulianDate &rhs) const
	Compare if chronologically after than another time point.
bool	operator<= (const JulianDate &rhs) const
	Compare if earlier than or same as another time point.
bool	operator>= (const JulianDate &rhs) const
	Compare if after than or same as another time point.

Public Attributes
double	jd
	Fractional number of days since the epoch (4713 B.C.)
double	jd_frac
	Smaller fractional number of days.

Detailed Description

Represents a specific point in time on the Julian calendar.

Generally not constructed manually, but instead converted from a DateTime or from Satellite::epoch. Supports some basic manipulation operations. For a human readable representation, can be converted back to DateTime. As for what time point this represents, see the comment on DateTime.

Internally, this is represented as the "theoretical" sum of two double precision floats. This is to preserve as much time accuracy as possible, since many bits are lost due to storing the number of the day. The smaller value is used to represent a more accurate time offset from that day. The "normalized" value restricts the larger value to entire days and the smaller to a [0.0, 1.0) time offset.

Constructor & Destructor Documentation

JulianDate() [1/2]

perturb::JulianDate::JulianDate ( double  jd, double  jd_frac  )

explicit

Construct from a Julian day number and fractional day.

The "true" Julian date value is the sum of the two. The motivation for separating into two parts is to preserve floating-point precision.

Parameters

jd	Larger Julian day value since epoch
jd_frac	Smaller fractional Julian day value

JulianDate() [2/2]

perturb::JulianDate::JulianDate ( DateTime  t )

explicit

Construct from a DateTime time point.

Precondition

Only years from 1900 to 2100 are supported.

Warning

The date and time are assumed to be valid, with no checks.

Parameters

t	Time point, must be from 1900 to 2100

Member Function Documentation

normalize()

void perturb::JulianDate::normalize

(

)

Normalizes a Julian date representation to a canonical representation.

Modifies the two julian day values to restrict the larger value to whole days and the smaller value to a [0.0, 1.0) time offset. This is not needed for the conversions as they will automatically normalize, but you may want to do this for other reasons.

operator+()

JulianDate perturb::JulianDate::operator+

(

const double &

delta_jd

)

const

Returns another time point offset by a number of days.

Offset is only added to jd_frac, so the returned value may not be "normalized". This needs to be done explicitly if desired. This could split delta_jd into a whole and fractional part and then add each accordingly, but I defaulted to the former method for performance. If you think this wasn't the right move, lemme know.

Parameters

delta_jd

Number of fractional days to add

Returns

Sum of a time point and offset, not normalized

to_datetime()

DateTime perturb::JulianDate::to_datetime

(

)

const

Convert to a DateTime representing the same time point.

Returns

Same time point converted to a human readable representation

---

The documentation for this struct was generated from the following files:

• /github/workspace/include/perturb/perturb.hpp
• /github/workspace/src/perturb.cpp