Apple Numbers program, weird thing with unix time code formula
Numbers '09 has a drop-down menu to specify the way that the time is shown in a Date and Time cell format.  The default in this situation seems to be None, but you can change it, as I show in the screenshot.



From your screenshot, however, I think you are using a newer version of Numbers.  I don't know where this setting is in that version, sorry.

One more thing: I think the last part of your formula +(-5/24) is perhaps correcting for a local timezone difference from UTC.  I'm not sure, but you may need to change this when daylight savings time stops or starts: worth making a note to check this on that date.