When we have a group of papers and when we fix the present time we can determine the unique number h being the number of papers that received h or more citations while the other papers received a number of citations which is not larger than h. In this paper we determine the time dependence of the h-index. This is important to describe the expected career evolution of a scientist’s work or of a journal’s production in a fixed year. We use the earlier established cumulative nth citation distribution. We show that ( )( ) 1 1t h 1 a T α α− = − 1 Permanent address Key words and phrases: Hirsch index, h-index, time dependent, Lotka, aging rate.