Time

Time is a hard concept to define.

Time is measured in Seconds, Minutes, Hours, Days, Weeks, Fortnights, Months, Years, Decades, Centuries, Millenniums, Ages, Epochs, etc.  

Most people seem to think that time always goes forward at a constant rate and that time is a continuum.

Time may actually be incremental and increase in specific units of time, perhaps on the order of about 10^-44 seconds per tick.

Western thought seems to consider time to be always advancing while some Eastern thought seems to consider time to be cyclical in nature.

The SI unit of time is the Second.