Clocks and Time

Intro

• Absolute Time - A specific time. e.g. 10AM.
• Relative Time - A value expressed as relative to some other time value (usually the current value). e.g. 10000 milliseconds.
• Standard Java only has a wall clock - calendar time. But real time systems require:
  • A monotonic clock.
  • A countdown clock.
  • A CPU execution time clock.