A new moon starts the lunar cycle, so a waxing crescent moon is considered to be a young moon because it is first seen in the western evening sky after new moon. A waning crescent moon is regarded as an old moon because it’s last seen in the eastern morning sky before new moon. For a write-up on the new moon, go to http://earthsky.org/moon-phases/new-moon.

Bruce

In fall, for example, the crescent moon will appear to one side of the sunset – and in spring it will appear directly above the sunset. So a young moon is easier to spot in spring than in fall. You can see a springtime young moon a day or two sooner than you can see the young moon in fall.

There are subtle variations for every month of the year. I’m afraid I don’t know of an online illustration of this phenomenon. I believe there is an illustration in a book called Astronomical Companion by Guy Ottewell. You can also learn by observing throughout the year. Stand in one spot, and draw the location of the earliest young moon you see with respect to the sunset – month after month – for a year. You will see the differences.

I hope this is helpful!

Deborah