The absolute date is like 12 or 13 days into the season. But you usually give yourself another week to give plausible deniability, because holding him down purely for service-time reasons is against the rules and he can file a grievance to get the service time restored. Pretty sure this is the correct answer, folks. To get super technical, a year of service time is 172 days. That's also the most you can accrue in any given season. The season typically lasts 183 days, but that can vary a bit from year to year. This year, it runs from April 5 to Oct 4, which is exactly 183. So as of April 17, there will only be 171 service days available left in the year. So that's technically the earliest they could call him up, except for the grievance thing.