Do you have a source backing the statement that daylight savings time improves energy conservation? I've used to live there and I know that lots of low income

Do you have a source backing the statement that daylight savings time improves energy conservation? I've used to live there and I know that lots of low income workers have to get out really early to commute from their satellite cities towards hubs like Sao Paulo. Talking about people who leave home around 3 to 4 AM. What are the physical and mental health consequences to this people? I don't know man but it sounds absolutely cruel.