Note: While the Legacy is currently offered only as a sedan, it was available as a wagon from 1994-2007. If you are looking for information on the Subaru Legacy wagon, click here.
The Legacy was refreshed for 2015. There are 2 notable changes. First is that the buckles for 2D & 2C are encased together in a rubber housing. Second is that Subaru now allows borrowing of the innermost lower anchors to secure a car seat in the center seat with LATCH – learn more about this type of center LATCH here. Otherwise the back seat is identical to the previous model year range.
This back seat continues to be very favorable for fitting 2 side-by-side or 3-across (so long as all the seats are narrow) as there is no seat belt overlap and the back seat is fairly wide and flat across. 
The Legacy sedan was redesigned for 2010.
The shoulder belt for 2C is no longer detachable – which is good because now there is less seat belt hardware to interfere with a car seat installation.
The head restraints no longer protrude like they did in previous models – and they remain removable for all three positions.
The four lower anchors are now hidden behind individual fabric flaps that must be unvelcroed and pulled down.
This back seat is very favorable for fitting 2 side-by-side or 3-across (so long as all the seats are narrow) as there is no seat belt overlap and the back seat is fairly wide and flat across.
For 2008, the plastic doors hiding the lower anchors in the previous model year were replaced by a large fabric flap that you have to unvelcro and pull down to reveal the lower anchors. Otherwise, the back seat is the same as 2007. 
Note: the Legacy sedan & Outback sedan of this model year range are essentially the same vehicle, and have the identical back seat.
For 2007 there were 2 changes (otherwise the back seat remains as it was for 2005-2006):
The lower anchors are now encased behind a plastic trap door – this can affect installation as it sometimes forces the lower anchor connectors (the hook on the car seat’s lower anchor strap) in a more horizontal position than it wants to be – and doesn’t allow the strap to orient itself vertically as it typically needs to allow the car seat to get tight.
The shoulder belt for 2C is now detachable – which creates extra seat belt hardware where it connects, which can interfere with a secure installation of some car seats.
Note: the Legacy sedan & Outback sedan of this model year range are essentially the same vehicle, and have the identical back seat.
For 2005, the buckles for 2D & 2P got much shorter and are now mostly rigid – but 2C remains flexible and on a long seat belt webbing stalk. For 2C, you will almost certainly find the need to twist the buckle stalk (up to 3 full revolutions) to shorten it in order to get many car seats installed tightly – as shown here.
The head restraints for all 3 seats protrude forward and will need to be removed when installing a forward-facing car seat or high back booster.
Note: the Legacy sedan & Outback sedan of this model year range are essentially the same vehicle, and have the identical back seat.
New for 2001, the Outback sedan gains lower anchors (LATCH) for 2D & 2P. Otherwise the back seat is identical to the 2000. 
Note: the Legacy sedan & Outback sedan of this model year range are essentially the same vehicle, and have the identical back seat.
The Legacy was redesigned for 2000 – it now has shoulder belts AND adjustable, removable head restraints for all 3 seats in back (it was very progressive!), as well as tether anchors for all 3 seats.
The seat belt buckles for all 3 seats are on VERY long pieces of seat belt webbing – you will almost certainly find the need to twist the buckle stalk (up to 3 full revolutions) to shorten it in order to get many car seats installed tightly – as shown here.
This model year range features shoulder belts in 2D & 2P, but only a lap belt in 2C. There are rudimentary head restraints in 2D & 2P, but no head restraint at all in 2C.
The seat belt buckles for all 3 seats are on VERY long pieces of seat belt webbing – you will almost certainly find the need to twist the buckle stalk (up to 3 full revolutions) to shorten it in order to get many car seats installed tightly – as shown here. 
