As student homelessness grows, little is known about how the timing and duration of homeless experiences shape K-12 outcomes. Using Los Angeles Unified School District administrative data, the authors examine whether these temporal dimensions of homelessness predict students' achievement and attendance. The authors find that homeless students scored lower on math tests and missed more school days than students who were never homeless. These associations are largest when students experience homelessness in the year the outcomes are measured. Experiencing homelessness in only 1 year and in 2 or more years both negatively predict outcomes, but associations are larger for students experiencing homelessness in only 1 year.