Gathering times are based on Eorzean time, not real world time. There would be 40 different spawn times to list if real world times were being used. That would be messy.

You can display Eorzean time next to your local/server time in your HUD by going to Character Configuration - UI Settings - HUD then scrolling down to Clock Type. You can toggle them on/off individually.

If you're going to AFK and want to know when you need to be back for the next spawn, one Eorzean hour is roughly 3 real world minutes. If you see the current Eorzean time is 1pm and your node spawns at 8pm, you want to be back within 21 minutes.