In the realm of construction within developing countries, the impact of substandard planning on project duration is a critical concern.The construction sector in Libya faces numerous challenges, including political instability, resource constraints, and outdated planning methodologies.By analyzing case studies and identifying common planning deficiencies, the study seeks to offer insights and recommendations for improving planning practices.Libya, a country striving to rebuild and expand its infrastructure, provides a pertinent case study for examining this issue.The ultimate goal is to enhance the efficiency and effectiveness of construction projects, fostering sustainable development in Libya and similar contextsThese factors contribute to prolonged project timelines and budget overruns, impeding the nation's development efforts.Poor planning practices often lead to delays, increased costs, and compromised quality, which can significantly hinder progress.This research aims to explore the influence of substandard planning on the duration of building development projects in Libya.This issue is especially pronounced in building development projects, where the complexities of construction demand meticulous planning and execution.