Spectro Magic always Starts on Main Street and ends in Frontierland (even when there are 2 performances in one night... they both start on Main Street). This way the exit is not blocked. If they were to start it in Frontierland the people watching it there or in Liberty Square would be blocked from exiting the park. By starting it on Main Street it is going away from the exit so as to not cause mass chaos. The ONLY time that Spectro starts in Frontierland is if they are filming it for something. This is very rare (probably only 2-3 times a year), this way as it comes down Main Street the castle is behind it...
So... Day Parade always starts in Frontierland and ends on Main Street....
Night parade always starts on Main Street and ends in Frontierland.