MILPERSMAN 1800-020 outlines the policies and procedures for determining the effective date of retirement for Navy personnel. This instruction specifies how to establish the official retirement date based on various factors, including service length, type of retirement (voluntary or mandatory), and any applicable regulations. It also provides guidance on the necessary documentation and processes required to ensure that the retirement date aligns with military requirements and personnel readiness. The goal of this instruction is to facilitate a smooth transition for service members into retirement while ensuring compliance with Navy policies.