The Time index behaves like any other Analytica index. It can be used as a dimension for arrays and tables, referred to by identifier in expressions, and operated over in array functions. In addition, Time provides an extra functionality not available to other indexes -- its use with Dynamic.
Dynamic models compute the value of a variable from the values of itself or other variables at earlier points in Time. Dynamic loops between variables, creating cycles on the influence diagram, are then possible. This ability to recur over the Time index is a very powerful feature of Analytica, and is something that is only possible over this special system index, Time.