  It seems logical to assert that the dynamic nature of software engineering
practice would mean that software effort estimation (SEE) modelling should take
into account project start and completion dates. That is, we should build
models for future projects based only on data from completed projects; and we
should prefer data from recent similar projects over data from older similar
projects. Research in SEE modelling generally ignores these recommendations. In
this study two different model development approaches that take project timing
into account are applied to two publicly available datasets and the outcomes
are compared to those drawn from three baseline (non-time-aware) models. Our
results indicate: that it is feasible to build accurate effort estimation
models using project timing information; that the models differ from those
built without considering time, in terms of the parameters included and their
weightings; and that there is no statistical significance difference as to
which of the two model building approaches is superior in terms of accuracy.
