Consists of units like years, months, day, hours, minutes, seconds
Good examples would be months of the year, days of the week, etc
Length is measured as Duration
Useful for defining a set of pre-defined, related constants
Can be used in formal parameter list of a method
Can be used in switch statements
Time after the epoch is positive
Length is described as periods
Beginning is referred to as the epoch (1/1/1970)
Is a timeline measured in nanoseconds
Should be in all caps, since they are constants
Is considered regular calendar and time
Time before the epoch is negative