When it's time to bust out the headlight

Well, today was the first day of "lights required" on the commute in to work. 

A few months ago I was curious about when this day would arrive, so I did some quick internet research. Using timeanddate.com I put in my location, and looked at where the "civil twilight" plus 10 minutes intersected with my start time (San Francisco link here). Here is what I came up with for when light are needed in the Bay Area:

Lights required for 6:50a start time:
  • Oct 3 2018 to Nov 3 2018 (time change)
  • Dec 5 2018 to Feb 7 2019
  • Mar 11 2018 (time change) - Mar 24 2019
This isn't perfect, but should get you within a couple days. If it's dark and stormy or your commute takes you through unlit, shady streets you are for sure going to want lights at other times.

What about for the afternoon commute? In this case it's about what time you plan to be home vs what time you start the commute. I have two normal options so here they are:

Lights required if home by 5:45p: Nov 4 2018 (time change) to Jan 31 2019
Lights required if home by 6:50p: Oct 10 2018 to Mar 11 2019 (time change)

Oh yeah, and this is just for your headlight. When should you use your blinking red taillight? I'd say all the time!

If you want to calculate this for your specific times start with the links above. The screenshot below circles where to look for "civil twilight plus 10 minutes" for morning commute. For the evening commute look for the end of civil twilight and subtract 10 minutes.

Source: timeanddate.com


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