Manual Reference Pages - phase_of_moon (3)

NAME

phase_of_moon(3f) - [M_time] return name for phase of moon for given date (LICENSE:PD)

Synopsis
Description
Examples
Author
License

SYNOPSIS

function phase_of_moon(datin)

   integer,intent(in)            :: datin(8)
   character(len=:),allocatable  :: phase_of_moon

DESCRIPTION

Phases Of The Moon
This procedure is used to support the %p field descriptor for the fmtdate(3f) routine.
The moon circles the earth every 29.530588853 days on average, so pick a starting point and count. A new moon occurred at Julian date 2451550.1 (January 6, 2000, 18:14 UTC). Then it is easy to count the number of days since the last new moon. This is an approximate calculation.
There are eight generally recognized phases of the moon in common use

o new or dark

o waxing crescent

o first quarter

o waxing gibbous

o full

o waning gibbous

o laster quarter

o waning crescent

To calculate the phase of the moon simply divide the days since the last new moon by eight and select the appropriate phase.
Note that technically the four states (new, first quarter, full, third quarter) are events not phases. That is to say, the moon is technically only new for an instant.

EXAMPLES

Sample:

   program demo_phase_of_moon
   use M_time, only : now
   use M_time, only : phase_of_moon
   use M_time, only : moon_fullness
   implicit none
   integer             :: dat(8)
      ! generate DAT array
      call date_and_time(values=dat)
      ! show DAT array
      write(*,’(" Today is:",*(i0:,":"))’)dat
      ! the %p and %P fields are supported by fmtdate(3f)
      write(*,*)now(’The phase of the moon is %p, with a fullness of %P’)
      write(*,’(1x,*(a))’,advance=’no’)’The phase of the moon is ’,trim( phase_of_moon(dat)),’,’
      write(*,’(1x,a,i0,a)’)’with a fullness of ’, moon_fullness(dat),’%’
   end program demo_phase_of_moon

Sample output:

Today is:2018:11:3:-240:20:18:44:245 The phase of the moon is Waning crescent, with a fullness of -30% The phase of the moon is Waning crescent, with a fullness of -30%

AUTHOR

John S. Urban, 2015

LICENSE

Public Domain

phase_of_moon (3)

July 05, 2020

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