How The Actual Hell Is The Chest Cooldown Timer Calculated

So basically I went to fight Qira, and I scrolled to Ragni, and I logged off. Didn't play for about a week. When I got back on, the Loot Chest in Lusuco had a 25 minute cooldown (the one near the tunnel/passage to the main Nesaak Plains) and when I tried to lootrun Dernel, the chest had a 21 minute cooldown. So I wait for the Lusuco one and I lootrun Lusuco (I'm not familiar with Dernel route). Took me about half an hour. Server restart, I went to another world. But when I tried to open the Dernel chest, there was a 20 minute cooldown. Can someone please explain how the hell this works?

 

Okay so basically every time you open a chest four timers start counting down
The timer for T1s is 3 minutes, T2s is 6 minutes, T3s is 12 minutes, T4s is 24 minutes
The timers are always there and counting down and all four always reset every time you open any chest at all but they're not always active
They activate when you log into a class, so changing servers/switching classes means you'll have to wait out the timers to keep opening chests
So if you haven't opened any chests for a while and plan on switching servers to lootroute it's usually a good idea to not open any chests before you switch so you don't reset the timers and have to wait longer since even just touching a stray T1 will make you have to wait
You can also try to kinda evade the timers to some extent by incorporating a stream of lower-tiered loot chests into the start of your lootroute so you're still doing stuff while you're waiting out the T3-4 timers
I used to do that when I lootrouted a lot and got an Inferno from it at one point ^
Hopefully this answers your question, I just woke up so it might not make a lot of sense

 

Thanks!