A field study was carried out during spring season, 2015 at research area of University College of Agriculture, Sargodha and Adaptive Research Farm Karor (Dist. Layyah) to investigate the climate change impact on growth, development and yield of sunflower hybrids planting at different times. The experiments were comprised of three sunflower hybrids (Hysun 33, S-278 and SF-0046) sown at three different dates (29th Jan, 14th Feb and 1st Mar) under randomized complete block design (RCBD) with split plot arrangement. Hybrids were randomized in main plots and sowing dates in sub-plots. Maximum achene yield (4213.2 kg ha-1) was produced by Hysun-33 followed by SF-0046 (3721.4 kg ha-1) and S-278 (3531.3 kg ha-1). In case of sowing dates (29th Jan) performed best for growth, development and yield as compared to 14th Feb and 1st Mar. The APSIM (Agricultural Production System Simulator) Model was calibrated successfully by adjusting genetic coefficients by using data on phenology, growth and yield of sunflower hybrids of 29th Jan sowing. Average error of three cultivars in calibration of achene yield and total dry matter was (17% and 7.6) at Sargodha and (22 and 5.9) at Layyah location. Evaluation of model was done against the observed data of remaining two sowing dates. The average error between achene yield and total dry matter for 14th Feb was (9% and -9%) at Sargodha and (11.7% and -8.9%) at Layyah location. For 1st March error was (23.5% and -6.6) at Sargodha while, (-9.8% and -13.4%) at Layyah location. The climate change analysis describes the strong effect on sunflower production. The factors which were changed are temperatureand CO2. So, the model was sensitized at different temperatures and CO2 levels. The achene yield was increased averagely under all three concentrations (395 ppm, 480 ppm and 560 ppm) for sowing date 29th Jan and 14th Feb and decreased for 1st March at Sargodha while, at Layyah decrease averagely at both 14th Feb and 1st March sowing. However, in case of increase in temperature (1oC, 2oC, 3oC achene yield increased averagely for 29th Jan and decreased for 14th Feb and 1st March at Sargodha. While, at Layyah for both 29th Jan and 14th Feb yield showed increased and decreased for 1st March.