In which month of the year did ( the construction of the building begin ? I. The construction engineer correctly remembers that the construction began before September but after May and that particular month did not have 31 days II. The builder correctly remembers that the construction began after February but before October and the fact that that particular month did not have 31 says.

Data sufficiency questions are designed to check your ability to analyse & categorise information based on underlying concepts rather than calculations. So you should try to observe -  analyse and to find linkages between various statements rather soing lengthy calculations.