The study takes its initial bearings from the theoretical framework established by B. Comrie, D. Bickerton and J. Bernabé and presents an analysis of the functioning of the tense-modality-aspect system in simple and complex sentences of contemporary and historical Guyanese creole. Also examined are the complementary systems of aspectual modality and auxiliaries, the behaviour of modal verbs etc. The analysis is based on texts available in Guyanese creole and grammaticality tests conducted during two research sojourns in French Guyana in 1992. The findings prove that the tense-modality-aspect system of Guyanan does not conform to the proto-creole or basilectal system proposed by D. Bickerton. It is, on the other hand, notable for the surprising stability of the grammatical structures identified.