When must all men register for Selective Service?

All men are required to register for Selective Service at the age of 18. This registration is part of the United States' preparedness for a potential draft, ensuring that the government has a list of individuals who could be called upon for military service in the event of a national emergency. Registration is mandatory and must be completed within 30 days of turning 18.

The other age options do not align with the legal requirements for Selective Service registration. While individuals may be involved in other forms of government service or programs at younger ages, the specific requirement to register with the Selective Service system is set firmly at 18, making this age the key point of compliance for eligibility and civic responsibility.