A. Dehnokhalaji - Department of Mathematical Sciences, Tehran Teacher Training University, Tehran, Iran
N. Nasrabadi - Department of Mathematical Sciences, Tehran Teacher Training University, Tehran, Iran
N. A. Kiani - Department of Mathematics, Science and Research Branch, Islamic Azad University, Tehran, Iran

The main purpose of this paper is to determine the best performance time period of a system, consisting some DMUs, among some sequential time periods. This aim is satised by two proposed algorithms, the rst based on global Malmquist Productivity Index and the second is based on PPS frontiers.

DEA, Best Performance Time Period, Global Malmquist Productivity Index