Unicode U+1F319 "crescent moon", it exists on OS X but it significantly different from the Windows version (yellow and orange shading vs solid white silhouette).

Since the visual appearance matters here more than being searchable by "", drawing the shape in CSS would be more consistent: http://aamirshahzad.net/moon-with-css3/

EDIT: Pretend there's a moon in those quotes. HN strips some Unicode characters, including that one.

The Symbola font[0] which is included in the Debian (and Ubuntu) package ttf-ancient-fonts[1] have that glyph and lots of other emojis--which is a very useful install if you want to see them in Linux. (So, I can see the crescent moon in Linux.)

[0] http://users.teilar.gr/~g1951d/ [1] https://packages.debian.org/jessie/ttf-ancient-fonts

it's in android