A friend challenged me to find the longest (by distance or time) commercially available flight (i.e. not just technically possible) that departs and arrives in the same time zone. There are no restrictions on flight paths that involve changing time zones, but the plane can't stop along the way, and flights between two adjacent time zones with different daylight saving protocols don't count. The best I could do was a rough tie between LIM-EWR/YYZ and LAD-CDG, each of which is around 8 hours. Apparently there aren't any direct flights between Perth and Beijing, St. Petersburg and Dar Es Salaam, or Jo'burg and Helsinki. Go figure.

Can anyone do any better?