I'm working through an animations tutorial which introduced closures. I began to search through Apple's reference docs for what TimeInterval is. I'm curious to know what is sub-millisecond precision?
It means it is more precise than 0.001 seconds (one millisecond or one one-thousandth of a second). You can store a value such as 0.0005 (five ten-thousandths or half of a millisecond).