I watched an ad to double my darwinium collection before the attached video. After I collected that and switched to the event, the timer reset to 4 hours again.
The timer does not reset to the proper time of 1:30 hours after I log back in after a few minutes. The timer does not reset to 4 hours when the tank is empty.
I'm not sure if this also happens when I switch to beyond or mesozoic valley, but I rather not test this too much as a f2p player who desperately needs all the darwinium they can get with all the new updates.