We use administrative data to examine how "clock" policies--program time limits and recurring deadlines for confirming eligibility--affected participation in South Carolina's TANF and Food Stamp Programs from 1996-2003. South Carolina's TANF program limits most families to two years of benefits in any ten-year period; so, recipients began exhausting their eligibility as early as 1998. The state's Food Stamp Program sets regular recertification intervals that can be distinguished from other calendar effects and increased these intervals after October 2002. We find that the two-year time limit reduced TANF caseloads and that the longer recertification intervals increased food stamp caseloads. (Contains 7 tables, 10 figures, and 4 footnotes.)