It’s Julian day 2460666!
Time for the end-time preachers to dust off their 'The End is Nigh' signs! But honestly, I think it’s just a great day to explore some interesting systems of keeping track of time!
For those who don’t know, the Julian Day Number (JDN) is a continuous count of days since the Julian calendar began on January 1, 4713 BCE. It’s used by astronomers and historians to simplify date calculations across different calendars.
So, while some might panic, I’m just here for the cosmic fun! 

I even wrote a simple shell function to get the Julian Day Number for today or any given date:
```
fish
function jdn
# Get the date from the argument or use the current date
if test (count $argv) -eq 0
set date (date -u +%Y-%m-%d) # Use current date if no argument is provided
else
set date $argv[1] # Use the provided date
end
# Convert the date to seconds since epoch
set seconds (date -u --date="$date" +%s)
# Calculate JDN using the formula
set jdn (math "$seconds / 86400 + 2440587")
echo "Julian Day Number for $date: $jdn"
end
```
Just a note: this function only works with dates UNIX time 01.01.1970 so it won’t apply to dates before.