Across sleep medicine, chronobiology, and publicโhealth research, the consensus is clear:
Human circadian rhythms synchronize to natural light, especially morning light.
Standard Time aligns civil time with solar time โ meaning sunrise, solar noon, and sunset occur closer to when your internal clock expects them.
DST delays morning light, which pushes your biological clock later and makes waking up harder.
This mismatch increases circadian disruption, sleep loss, and metabolic stress.
Stanford Medicineโs modeling found that permanent Standard Time would benefit the most people, reducing stroke and obesity rates compared to DST or switching twice a year.
Sleep experts also warn that DST causes circadian misalignment, especially in spring, because the abrupt shift alters natural light exposure patterns.