Precession

Fred Seward writes (via FFC):

The attached jpg picture [from Wikipedia] shows the precession of the pole with dates labelled. The circles of declination are spaced every 15 deg.  In 176 years the pole will travel 1 deg away from the N star, or 5 deg in 880 yr.  This corresponds to 1120 AD.

This is true if your alignment is on the N star.  If it is on the autumnal equinox, the geometry is more complicated.  In this case, 5 deg will take you back to 1600.  probably earlier for the vernal.