Results from a correlation analysis of Wind and IMP 8 magnetometer data for a total of 543 two hour periods covering Jan--Jul 1995 were analyzed to determine that: (1) the timing accuracy Δ&tgr; for advecting solar wind magnetic field structures goes as (dper/dpar)⋅&tgr;con where dpar is the spacecraft separation along the Sun-Earth line, dper is the transverse separation, and &tgr;con is the predicted convection lag time, (2) good correlation time periods (peak correlation coefficient >0.80) are about twice as likely at solar maximum than at solar minimum, (3) geometry affects timing accuracy more than any propagation of features with respect to the solar wind, and (4) there is a high probability (greater than predicted by a Gaussian distribution) of very bad (|dparΔ&tgr;/dper&tgr;con|>3) timing agreement due to the long tail on the probability distribution. ¿ 1998 American Geophysical Union