This paper advances a theoretical framework on the impact of time rules on the administrative coordination of policies that deal with long-term, transboundary challenges. Its empirical focus is on the fight against antimicrobial resistance—AMR. The paper’s framework concerns how government agencies employ time rules in coordination so as to respond to this open-ended policy challenge. To illustrate the framework’s usefulness to studies of coordination, the paper examines Sweden's intersectoral coordination on AMR. The case study draws on interviews and policy documents. Its findings give support to the paper’s argument, namely that government agencies are more likely to coordinate voluntarily if they have discretion in setting and administering coordinative time rules.