Anyways, this has created a new need in our life. It turns out that since we bike after work, we need to know precisely when the daylight will give out, so we can be sure to leave work with enough time to change clothes and get on those fat tires. (Living in Miami, there are actually gators in our neighborhood. I’ve never seen one, but I’m still too afraid of ’em to be wandering around at night).
Anyways, I set my inquisitive mind to this task, and figured out how to know exactly when it’ll be dark outside. Here’s how it goes.
What Time Does Night Start?
It turns out that, in terms of light and time, the setting of the sun is divided into five phases: day, civil twilight, nautical twilight, astronomical twilight, and night. There are technical definitions for each, but I’m here to tell you how to find out when each starts, and what they actually mean in terms of the light you’ll see outside.
What is Civil Twilight?
After the sun sets, there is still sunlight for a while in the form of twilight, when the upper atmosphere reflects sunlight back onto the earth. Civil twilight is the earliest twilight phase. To me, it still looks like day, or what we would call late afternoon. Take a look at the beginning of civil twilight:
If you are still doing an activity that requires daylight, I’d say that this would be when you should start wrapping up, since civil twilight may only last about 20-30 minutes.
What is Nautical Twilight?
This is basically what we would call the threshold between day and night, when it’s kind of dark outside, but you can still see. Probably when you would turn on your car headlights, if you haven’t already.
Like civil twilight, nautical twilight lasts around 20-30 minutes.
What is Astronomical Twilight?
For our purposes, it’s night. You can’t see much outside, and it’s just dark. It might not technically be night, but to my eyes it is:
So When Does Night Start?
For non-scientific purposes, and in my view, you can’t really do daytime activities anymore once it’s around 10-15 minutes past civil twilight or, at most, once it’s nautical twilight. So again, I suggest that you start wrapping up and calling your kids in and whatnot right around civil twilight.
How Do I Know When These Times Are?
To find out the times, just Google the name of your city, followed by “twilight hours” or something like that. You should get a result from the Time and Date website showing you the exact times. For example, these are the New York City times for March 15, 2018:
If you have an iPhone, you can also ask Siri “what time is dusk?”, and she’ll give you the end of daylight/start of civil twilight.
Summing It Up
So file this one under “life hacks”, dear readers. If you’re planning an activity that you need to do when there’s still light out, you can know exactly when that’ll be by finding out this information. Remember, once it’s civil twilight, you’ve probably got less than an hour until it’s dark, and it’s probably time to wrap up. Put another way, you’ve still got a little slack after daylight ends, but just enough to finish things up.
Have you ever used twilight data for your activity planning? Do you also fear night gators? What kind of fearsome fauna inhabits your area?