Daylight/Night clock

[ylub]

I have a python script that displays the regular time as well as the time based on daylight (calculated either sunrise to sunset or halachic daybreak to nightfall) for locations based on zipcode and coordinates currently . It is mostly for curiousity's sake but it does have some uses.

Would this be a potential feature in some form for linecast?

[ashuttl]

Interesting, maybe! It's pretty. I need to read up on Halacha.

[ylub]

In a nutsh the times when one may recite certain prayers are calculated by dividing daylight or night into 12 "hours" which, depending on the time of year and geographical location, will be more or less than the 60 minute hour we are used to. There are two main ways this is calculated: sunrise to sunset, and daybreak (10.2 degrees, or a fixed period of standard minutes according to some) to nightfall (calculated similarly).

As a curiosity item, it would be interesting to know something like when 25% of the day has passed (9:00 or 3:00, depending on if the beginning of day is considered 00:00 or 06:00).

Just to clarify - my suggestion was including the calculations/time perhaps in the sunlight or moon commands not specifically the cli display (which I would also be glad to make public).

Thanks again for linecast!

[ashuttl]

Oh I gotcha. It's a very good idea, and moon and sunshine seem like the natural places for it. I'm going to do some more research on the particulars and how I'd calculate it while I mull over how to present it.

I'm also going to look into what other cultures might benefit from a similar calculation – I'm thinking of the Islamic prayers and Ramadan fasting progress, of the ancient Roman seasonal hours, and wadokei.

This is a great fit for what I'm trying to do! Thank you very much for the suggestion.

[ashuttl]

And @ylub could I see your script? I've done some reading now and I'd love to see (or even just hear from you) how you're calculating the times.

[ylub]

Here is the package of it (it is part of a larger program for more specific "halachic" times for various services etc.): Halachic Clock v1.0.0.

It calculates sunrise and sunset locally from latitude, longitude, and timezone. "GRA¹" mode defines the day as sunrise to sunset; "MGA²" mode uses 72 minutes before sunrise through 72 minutes after sunset. That interval is divided into 12 equal "halachic hours" mapped onto a 12-hour clock face. Night uses the interval between one day’s end and next day’s start.

Footnotes

1. Hebrew abbreviation for The Vilna Gaon, a halachic authority who espoused this approach of calculating "halachic day". ↩

2. Abbreviation for Magen Avraham, a halachic authority who espoused the other position. (I can get you exact dates and more info about these authorities if you would like) ↩

[ashuttl]

Thank you for sharing this @ylub!

This is in 2.7.0, released today. Thank you for the idea, and for the script, which was a real help in seeing how it should be counted.

sunshine --hours halachic reads the day in sha'ot zmaniyot beside the civil clock, and linecast hours halachic saves that as a preference so you don't need the flag. The top-left corner of the day view shows the hour and how far through it you are. A line under the chart lists the day's zmanim in order (if they fit in your terminal), with the next one counted down. --json gets the same as ISO times, with the Hebrew names. --oneline gets them too.

I did it the two ways you described. halachic is the Gr"a, sunrise to sunset. halachic-mga is the Magen Avraham, alot to tzeit at 72 fixed minutes either side, like your script. The night is twelve hours the same way. The marks use the angles from Hebcal and KosherJava (16.1° for alot, 11.5° for misheyakir, 8.5° for tzeit). I checked results against Hebcal's API to the second for Jerusalem, Brooklyn, Helsinki, and Melbourne on the equinox and the solstices.

There's more detail in HOURS.md. I would be very glad to know if any of it is wrong or not useful to someone who actually uses these times, or if there's any other way you see that this could be made more useful or lovely.

[ylub]

My pleasure glad to help!