julian

#!/bin/bash

#################################################################################################################################
# Modified Julian Date can be read about at http://en.wikipedia.org/wiki/Julian_day						#
#																#
# This realtime clock converts the current date to Modified JD and displays both in realtime.					#
#################################################################################################################################

function juliantime()
{
	# Get the current date and time components just once
	todayis=$(date +"%F")
	hourtime=$(date +"%H")
	minutetime=$(date +"%M")
	secondtime=$(date +"%S")

	# Compute Julian Day once outside the loop
	let julian=(`date +%s -d $todayis`-`date +%s -d 1968-05-24`)/86400+40000

	# Infinite loop for real-time conversion
	while true
	do
		# Re-fetch the time in the loop
		hourtime=$(date +"%H")
		minutetime=$(date +"%M")
		secondtime=$(date +"%S.%N" | head -c10)

		# Compute Julian time as a float
		juliantime=$(echo "scale=9; ($hourtime / 24) + ($minutetime / 1440) + ($secondtime / 86400) + $julian" | bc -l)

		# Clear the screen and display results
		clear
		echo "Standard Gregorian Date"
		echo "$todayis $hourtime:$minutetime:$secondtime"
		echo "Modified Julian"
		echo "$juliantime"

		# Sleep for a small fraction of a second (to update frequently without excessive CPU usage)
		sleep 0.01
	done
}