With the advent of the Time Wars, the national armies of the world restructured themselves into temporal versions, fielding troops into the emerging conflicts conducted throughout Minus Time, as part of the adjudicated actions overseen by the Referee’s and factored into the Point Spread that determined the victory of disputes in Plus Time. The US Army Temporal Corps, overseen by the Ministry of Defence, was one of those national forces.
US citizens at age 17 are given a mandatory series of test the Service Aptitude Test (S.A.T’s) used as an indicator of intelligence and potential, allowing for some to advance into careers in the private sector, or any number of other options, including enlisting at various levels of service.
Service time is arguably a bit of a hard thing to compute, but to break it down, you enlisted for a term of service of one week. This seems like a simple and quite short period of time, unfortunately the Army only counts Plus Time, towards that total. In practice you could Clock Out at 9:30 in the morning, to spend 10 months slogging through the trenches of World War One, only to Clock Back at 9:35, having only spend 5 minutes away of Plus Time adding towards your service. Wounds sustained on missions can grant the solder the option of taking bonus time, paying extra time towards their term of service, or the ability to exercise an option to choose a mission assignment, rather than seemingly random selection.