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A rapid climatic change has threatened the productivity of many field crops across globe including Pakistan. Suitable sowing time is imperative for yield enhancement and sustainability under unpredictable climatic conditions. Bt cotton is cash crop of farmers in central and south Punjab, Pakistan. However, there exists the problem of sub and supra optimum temperature in cotton growing regions of Pakistan which negatively impacts the seed-cotton yield. Thus, there is dire need to optimize the sowing time of cotton in central and south Punjab. This 2-year study (2013 and 2014) was conducted to evaluate the best sowing time of different Bt cotton cultivars under different climatic conditions of Punjab. The experiment consisted of three Bt. cotton cultivars (viz. BH-184, CIM-598, MNH-886) which were sown at five sowing dates (viz. March 01, March 15, April 01, April 15, May 01, May 15) at three experimental sites (viz. Faisalabad, Multan, Bahawalpur) with three replications. The results indicated that Bt cotton sown on 15th April produced the highest seed yield (3044 kg ha(-1)) and showed the better fiber quality than all other sowing dates owing to increase in yield related traits (number of sympodial branches, bolls per plant and 100-seed weight); while crop sown on 1st March didn't performed well. MNH-886 produces highest seed cotton yield (3044 kg ha(-1)) at Multan. There was a positive correlation of growth and yield related traits with seed cotton yield. In conclusion, sowing of Bt cotton on 15th April is the best option to harvest higher seed cotton yield under arid to semi-arid conditions of Punjab, Pakistan.