[amsat-bb] GPS Time observation

I have an old GPS unit, a Magellan explorist 210. It's fairly accurate determining position. After it has acquired about eight to ten satellites the position error averages between 20 to 35 feet. Now the question, the other day I was looking at one of the information pages the unit can display and on it, it gives the time in UTC. Just for fun I thought I would see how close the time was to WWV. I was surprised to see the unit was between one to four seconds off over various tests compared to WWV. IS this typical of all GPS units or do some display the time of day more accurately?

KB7ADL