- Days, for:
- the regular flow of the game in the top right corner
- research speed
- most or all economic statistics?
- ship maintenance
- diplomacy trends
- trade income in the diplomacy screen
- population growth [probably annual?]
- most economic statistics
- mining rate
- estimated resource demand
- construction & repair time/speed
- everything in the ship design menu other than maintenance
But what on earth do the "per second" figures mean? I assume they can't be game-time, because then you'd need to multiply every figure by x86400 to work out how many days it is and give you a figure that means something in the context of the rest of the game. But it can't possibly be real-time either, because there are 5 different speed settings for the game, and even at normal speed, the game will run faster or slower depending on your hardware, the size of the galaxy, how buggy it is, etc etc.
So is the use of 'per second' just a mistake/oversight? Should it be "per tick" or "per day"? And if the former, how many ticks are there in a game-day? As it is, there are vast swathes of crucial data in the game that are completely impossible to contextualise.