4 ms·

I have two questions that I will ask as two separate comments. My first question: How does forwarding the clock by 1 hour in summer give one extra hour of dayl

I have two questions that I will ask as two separate comments. My first question: How does forwarding the clock by 1 hour in summer give one extra hour of daylight? Say, without DST on a certain summer day, the sun would normally (without DST) rise at 5 AM and set at 7 PM. Also, say that I normally work from 9 AM to 6 AM. Without DST, I am working when the sun is there. With DST in effect (clock being one hour forward), the sun would rise at 6 AM and set at 8 PM my 9 AM to 6 AM working hours still fall within the time when the sun is there. What is gained? Can you give an example of times and working hours that demonstrates the usefulness of DST in summer?

1_player 10y ago
> the sun would rise at 6 AM and set at 8 PM > 9 AM to 6 PM working hours It wouldn't affect your working hours, but you'd enjoy one more hour of sunlight after work (instead of sunset at 7 PM without DST). Personally going home from work when the sun is still up makes me feel I still have a lot of time to do stuff, and conversely, I hate going to work when it's still dark, and/or coming home from work when it's dark already.
hvjackson 10y ago
The purpose is to put more of the daylight hours in the evening when people are able to enjoy it. And/or when it may reduce the use of electricity (though studies show it probably doesn't have much or any effect). If the sun rises at 5am, few people will be awake to take advantage of that light, so shifting it to 6am has not much effect. But shifting sunset from 7PM to 8PM gives people an extra hour of daylight in the evening.
suvelx 10y ago
If the sun sets at 8pm 'real', and 9pm DST, most people get an hour more daylight. Vs, the sun rising at 5am 'real', and 6am 'dst' when everybody is asleep and wants it to be dark.
Ophiom 10y ago
Taken straight from Wikipedia: Putting clocks forward benefits retailing, sports, and other activities that exploit sunlight after working hours, but can cause problems for outdoor entertainment and other activities tied to sunlight, such as farming. It additionally mentions that DST was most heavily implemented during the energy crisis of the 70's.
- JoeAltmaier 10y ago
  Farming has no problem with DST. They work from dawn to dusk (and beyond) regardless of the clock.
  - astrodust 10y ago
    Everyone parrots that DST is for farmers, as if livestock look at the clock before going about their business. It's for factory workers. It always has been.
mikeash 10y ago
Most people wake up with just enough time to prepare and go to work to arrive on time. They go to bed at whatever time gives them enough sleep given the time they'll wake up. For your example, imagine it takes you 30 minutes to get ready in the morning, and 30 minutes to commute. You wake up at 8AM, leave at 8:30, arrive at 9. You get done with work at 6PM and return home at 6:30PM. You go to bed at midnight, giving you 8 hours of sleep. Without DST, the sun rises at 5AM and wasted on you for three hours until you wake up at 8AM. You then return home at 6:30PM and benefit from 30 minutes of sunlight at home. With DST, the sun rises at 6AM and is wasted for two hours. You get 90 minutes of sunlight at home after work. Yes, the total amount of sunlight is the same either way, and you could rejigger your schedule to take advantage of it. But people don't.
rescbr 10y ago
The reason DST exists is to shift the electric grid peak load time. As the summer base load is larger due to air conditioning during office hours, you can postpone turning on the street lights by one hour while the offices turn off their air conditioning units, avoiding bringing up peak power plants just to supply this one hour demand.
- vonmoltke 10y ago
  Where do you live that office buildings turn their HVAC off except for maintenance? Sure, there is less load on the system when nobody is there, but it never shuts off.
  - rescbr 10y ago
    At least in southeast Brazil it is pretty common to turn off HVAC at night when the workers leave and turn it back on at sunrise, even large companies and buildings do this. I work at a giant multinational company and you have to request an exception for HVAC and lighting outside office hours.
  - mixmastamyk 10y ago
    Where I've worked the AC shut off every night at 8pm and on weekends, though I think it was on 8-12am on Saturdays. Got unbearable sometimes in the summer. (California)
  - amyjess 10y ago
    I used to work in Downtown Dallas: the building turned off their HVAC on weekends and holidays. I don't remember if they did the same for nights. But I distinctly remember that whenever a holiday was coming up, they'd post notices on every entrance warning that the building would be closed on the holiday, pointing out that you'd have to use your badge to enter and that HVAC would be shut off all day. Then again, that building was terrible. They operated on a shoestring budget. For example, they once cut water to the bathrooms for maintenance on a work day because they didn't want to pay more to have their maintenance people on a weekend. For another example, the elevators were scary and they were lax on maintenance: I've been stuck in them, most of my co-workers got stuck in them, and I've actually been in the elevator when it violently shook on the 6th floor and then slowly drifted to ground level. They were notoriously unprofessional, and they were literally the only property management company I've ever had to file a complaint with the city about (though it wasn't over their maintenance issues).

1_player 10y ago

> the sun would rise at 6 AM and set at 8 PM > 9 AM to 6 PM working hours It wouldn't affect your working hours, but you'd enjoy one more hour of sunlight after work (instead of sunset at 7 PM without DST). Personally going home from work when the sun is still up makes me feel I still have a lot of time to do stuff, and conversely, I hate going to work when it's still dark, and/or coming home from work when it's dark already.

hvjackson 10y ago

The purpose is to put more of the daylight hours in the evening when people are able to enjoy it. And/or when it may reduce the use of electricity (though studies show it probably doesn't have much or any effect). If the sun rises at 5am, few people will be awake to take advantage of that light, so shifting it to 6am has not much effect. But shifting sunset from 7PM to 8PM gives people an extra hour of daylight in the evening.

suvelx 10y ago

If the sun sets at 8pm 'real', and 9pm DST, most people get an hour more daylight. Vs, the sun rising at 5am 'real', and 6am 'dst' when everybody is asleep and wants it to be dark.

Ophiom 10y ago

Taken straight from Wikipedia: Putting clocks forward benefits retailing, sports, and other activities that exploit sunlight after working hours, but can cause problems for outdoor entertainment and other activities tied to sunlight, such as farming. It additionally mentions that DST was most heavily implemented during the energy crisis of the 70's.

JoeAltmaier 10y ago
Farming has no problem with DST. They work from dawn to dusk (and beyond) regardless of the clock.
- astrodust 10y ago
  Everyone parrots that DST is for farmers, as if livestock look at the clock before going about their business. It's for factory workers. It always has been.

mikeash 10y ago

Most people wake up with just enough time to prepare and go to work to arrive on time. They go to bed at whatever time gives them enough sleep given the time they'll wake up. For your example, imagine it takes you 30 minutes to get ready in the morning, and 30 minutes to commute. You wake up at 8AM, leave at 8:30, arrive at 9. You get done with work at 6PM and return home at 6:30PM. You go to bed at midnight, giving you 8 hours of sleep. Without DST, the sun rises at 5AM and wasted on you for three hours until you wake up at 8AM. You then return home at 6:30PM and benefit from 30 minutes of sunlight at home. With DST, the sun rises at 6AM and is wasted for two hours. You get 90 minutes of sunlight at home after work. Yes, the total amount of sunlight is the same either way, and you could rejigger your schedule to take advantage of it. But people don't.

rescbr 10y ago

The reason DST exists is to shift the electric grid peak load time. As the summer base load is larger due to air conditioning during office hours, you can postpone turning on the street lights by one hour while the offices turn off their air conditioning units, avoiding bringing up peak power plants just to supply this one hour demand.

vonmoltke 10y ago
Where do you live that office buildings turn their HVAC off except for maintenance? Sure, there is less load on the system when nobody is there, but it never shuts off.
- rescbr 10y ago
  At least in southeast Brazil it is pretty common to turn off HVAC at night when the workers leave and turn it back on at sunrise, even large companies and buildings do this. I work at a giant multinational company and you have to request an exception for HVAC and lighting outside office hours.
- mixmastamyk 10y ago
  Where I've worked the AC shut off every night at 8pm and on weekends, though I think it was on 8-12am on Saturdays. Got unbearable sometimes in the summer. (California)
- amyjess 10y ago
  I used to work in Downtown Dallas: the building turned off their HVAC on weekends and holidays. I don't remember if they did the same for nights. But I distinctly remember that whenever a holiday was coming up, they'd post notices on every entrance warning that the building would be closed on the holiday, pointing out that you'd have to use your badge to enter and that HVAC would be shut off all day. Then again, that building was terrible. They operated on a shoestring budget. For example, they once cut water to the bathrooms for maintenance on a work day because they didn't want to pay more to have their maintenance people on a weekend. For another example, the elevators were scary and they were lax on maintenance: I've been stuck in them, most of my co-workers got stuck in them, and I've actually been in the elevator when it violently shook on the 6th floor and then slowly drifted to ground level. They were notoriously unprofessional, and they were literally the only property management company I've ever had to file a complaint with the city about (though it wasn't over their maintenance issues).