||Wait: 1 ms to 49.7 days
||Simple programs, easiest to use
||Can't do anything while waiting
||Recurring timing functions
||Schedule work at regular intervals
||Must repetitively call check() function
|Variables that automatically increment
||General purpose: scheduling work, timeout waiting for input, etc.
||Variables must be outside functions. Avoid compare equals.
||Wait: 1 µs to 16 ms
||Short delays for hardware response
||Interrupts can lengthen delay
|Time since your code began
||Math & rollover handling required
||Function called at regular intervals
||Accessing hardware with precise timing
||Advanced interrupt programming is required
|Date & Time
||Keeping track of calendar time
||Extra hardware required to retain while power is off.