With the increased focus and importance placed on the twin green and digital transition, also the development of digital products and software systems must take environmental sustainability into account. At present, the environmental impact of software systems has gained more and more attention from both the software development and the software procurement side. Researchers have provided many conceptual models of green software, but there is a lack of comprehensive, contemporary models to cover the overall picture, the whole life cycle of software. Aim of this study is to present the Green Software Life Cycle (GSLC) model that incorporates sustainable practices and metrics. The model is formed by gathering promising practices and metrics from the existing body of knowledge and mapping them to the software life cycle phases. The theoretical model is then validated by interviewing software practitioners. The model encompasses the whole software life cycle, and should provide inspiration for not only to the software developers, but to all stakeholders who are participating the software life cycle and aim for more environmentally sustainable digital products. Although the GSLC model provides a starting point towards making the software life cycle greener, further refinement and empirical validation is necessary in the future.