  Blue stragglers and other mass transfer/collision products are likely born
with rapid rotation rates due to angular momentum transfer during
mass-transfer, merger or collisional formation. However, less is known about
the angular momentum evolution of these stars as they age. Here we compare
rotation rates and post-formation ages of mass-transfer products to models of
angular momentum evolution for normal main-sequence stars and collisionally
formed blue stragglers. In our sample, we include both F- and G-type blue
stragglers in the cluster NGC 188 and post-mass-transfer GK main-sequence stars
in the field, all binaries with WD companions. We compare ages derived from WD
cooling models to photometric rotation periods and/or spectral vsini
measurements. We demonstrate that these systems have rapid rotation rates soon
after formation. They then spin down as they age much as standard solar-type
main-sequence stars do. We discuss the physical implications of this result,
which suggests that the spin-down of post-mass transfer stars can be described
by standard magnetic-braking prescriptions. This opens up the possibility of
using gyrochronology as a method to determine the time since formation of blue
straggler stars and other post-mass-transfer binaries.
