DateTime::Astro - Functions For Astromical Calendars

DateTime::Astro implements functions used in astronomical calendars, such as calculation of lunar longitudea and solar longitude.

This module is best used in environments where a C compiler and the MPFR arbitrary precision math library is installed. It can fallback to using Math::BigInt, but that would pretty much render it useless because of its speed and loss of accuracy that may creep up while doing Perl to C struct conversions.

This module works, but there are several caveats you should be aware of:

There /is/ a HALF BAKED Pure Perl implmentation bundled with this distribution, but at this point please consider it UNUSABLE. This sort of calculation requires the speed and efficiency of a C library anyway.

As such, you HAVE to have MPFR installed correctly in your system. Please consult your local package manager, or http://mpfr.org

Patches to make the pure perl version work better is always welcome.

I've tried very hard to correctly calculate the solar term dates with this module, but I still get 17 instances in about 130 years worth of solar terms, where the dates are off by an average of about 5 minutes -- and these usually fall at right about midnight, causing day-based comparisons to be off by 1.

I'm sure there's something that's causing a round off somwhere. If you're up to it, please see xt/101_solar_terms.t and see if you can fix it for me!

Returns 'XS' or 'PP', noting the current backend.

Given a moment (days since rd + fractional seconds), returns a DateTime object in UTC

Computes the moment value from given moemnt, taking into account the ephemeris correction.

Computes the moment value from a DateTime object, taking into account the ephemeris correction.

Computes the ephemeris correction on a given moment

Computes year, month, date from RD value

Computes year from RD value

Computes the julian centuries for given DateTime object

Computes the julian centuries for given moment

Computes the lunar phase for given DateTime object

Computes the lunar phase for given moment

Computes the polynomical expression using $x as the variable. The left most argument is the constant, and each successive argument is the coefficient for the next power of $x

Computes the gregorian components (year, month, day) from the RD date, and the number of seconds from the fractional part.

Returns the Moon's longitude on the given date $dt

Returns the Moon's longitude on the given moment $moment

Returns the date $dt expressed in moment

Returns the $n-th new moon, in $moment.

Currently the new moons dates are accurate to about within +/- 60 seconds of the actual new moon for modern dates.

For older dates, the accuraccy degrades a bit to about +/- 5 minutes.

Returns the Sun's longitude on the given date $dt

Returns the Sun's longitude on the given moment $moment

Mean time (in moment) between new moons

Mean time (in moment) between a full year (time for the Earth to go around the sun)

This library is available under Artistic License v2, and is:

Copyright (C) 2012  Daisuke Maki C<< <[email protected]> >>

Daisuke Maki <[email protected]>