If their system is set up for local times, that would not be an unreasonable amount of time.

‘transshipment center’ sounds so wrong in 2026.

It’s called time zones, because the earth is round.

A flight is roughly 13 hours flight, dependingon the weather. The time difference is 15 hours (UTC+8 Shenzhen time and UTC-7 Los Angeles time).

So when you leave 8AM you can go back in time and arrive at 6AM the same day. But a flight that distance can also be longer due to weather conditions and/or waiting times during landing.