Is being ‘late for work’ illegal in the military?

Yes, the military is much more than a job. Things that would lead a civilian employer to simply fire an employee can lead to criminal punishment in the military.

Article 86 of the Uniform Code of Military Justice (UCMJ), 10 U.S.C. 886, makes it a crime to fail to go to one’s appointed place of duty at the time prescribed, to leave one’s place of duty, or to be absent from one’s unit without authority.

There is tremendous discretion vested in a military commander to determine what, if anything, to do about a particular violation.

Often a first transgression is dealt with by minor punishment, such as loss of leave, privileges, or extra work assignments. More aggravated cases may result in administrative discharge rather than by referral to court-martial. Intentional behavior, such as coming in late to miss deploying with his unit to an unpleasant location, can result in an unpleasant court martial. The military makes examples of people like that to encourage everyone else to attend wars and other things most folks would prefer to avoid.