Final answer:
Service members on duty before December 31, 2017, would be grandfathered into the High-3 retirement system, requiring adaptation to new benefits and regulations.
Step-by-step explanation:
Beginning on January 1, 2018, service members who were contracted to serve or were in service on or before December 31, 2017, would be automatically enrolled in the historical "High-3" military retirement scheme. Retirement benefits are computed under this system by taking the average of the years of service and the highest 36 months of base pay, which are typically the last three years of service. As people adjust to new roles at different stages of life, like becoming an adult registering for the Selective Service System or a senior accessing Medicare, so too do people need to socialize themselves into new benefits and regulations when a new retirement system is implemented.