The body's biological functions follow a circadian rhythm, meaning that individual biological functions in the body change over a 24-hour cycle. There is evidence suggesting that the body and cancer cells may react differently to anti-cancer treatment based on the time of day they are exposed. In fact, researchers have already found that giving anti-cancer treatments at a particular time of the day works better in rectal and ovarian cancer. Temozolomide (TMZ) is a chemotherapy pill/capsule commonly given to patients with newly diagnosed glioblastoma after brain surgery and radiation treatment. However, there is no current standard for what time of day TMZ should be taken for the treatment of glioblastoma. In the current study, participants are randomly placed in one of two groups: a morning group and an evening group. Based on this group placement, participants are instructed to either take their TMZ in the morning or in the evening and record the date and time they take their TMZ in a pill diary. The primary goal of the study is to understand if taking TMZ at a prescribed time of day (morning/evening) is feasible in adults with glioblastoma. This is a pilot trial, and the investigators hypothesize that it will be feasible for glioblastoma patients to take TMZ at the prescribed time of day. The secondary goals of this study are to evaluate participant recruitment, safety, health-related quality of life, and changes in condition over time. This pilot study will help investigators plan for a larger, pragmatic randomized clinical trial in the future.