Time Ghosts have knowledge from all times and can think without being bound by time, and therefore have an Intelligence increase of +2.  Because they are arguably immortal (being spread across all time) they are very hard to kill, gaining a +1 to Constitution.

As gravity is just a warping in Space-Time, Time Ghosts can choose to disregard gravity.  They have a hover ability - they can change altitude vertically, but have no lateral fly speed.  They can hover and then move sideways by interacting with the environment, such as by pulling on a rope or climbing along the ceiling.  This ability acts at all times.

Force damage acts directly on the space-time continuum, causing it to be particularly damaging to Time Ghosts.  Time Ghosts have vulnerability to force damage.

As Time Ghosts are not fully corporeal, hitting them with blunt objects doesn't work very well - to others, it's almost like the weapons go right through them.  They have a resistance to bludgeoning damage.

Time Ghosts have a continually shifting appearance, including clothing, as they shift between versions of themselves in different times and maybe even universes.

Thanks to their existence throughout time, Time Ghosts have knowledge of all languages.  However, it's difficult to access knowledge from the rest of the timeline.  Therefore, they can only speak Common, but can read any language, if given long enough - even extinct languages.

Time Ghosts are ageless.  They always appear to be the age they were when they became Time Ghosts.  If your Time Ghost is destablized between alternate universes, as well as time, they may also appear to be different ages.  Though their appearance may change, they do not actually age over time, and if left alone will never die.

Time Ghosts have a slight sense of what will happen in the next several seconds, even though they can't consciously see into the future.  As a result, they cannot be surprised and take half damage from traps.