The sunrise/sunset times, candle-lighting & havdalah times, moon phase information, Jewish holidays, weekly parshiot, and hebrew dates are all calculated programatically. This data is generated using (and subject to the limitations of) two well-known, freely available software packages:
- Remind Version 3.00.23, by David F. Skoll
- Hebcal Version 3.4, by Danny Sadinoff
The software packages have been customized for (East) Denver, CO (39°42' latitude, 104°54' longitude -- around Monaco & Alameda), and all displayed times reflect this location. Elevation is not factored into the sunrise/sunset calculations, and certain z'manim are derived (e.g., Havdalah, etc.) using "fixed minutes" calculations, as described below.
The Shabbos davening times are automatically generated and posted to the website each week on Sunday mornings. The monthly calendar is also dynamically generated with the Shabbos davening times calculated the same way, according to the algorithm described below (which has been approved by the Ritual Committee).
- Davening times are always rounded to the nearest 5 minute mark on the clock.
- Friday Mincha (erev Shabbos):
- The ideal target range for Mincha is considered to be from 6:05 - 6:55 pm, and during or around this time range, Mincha is called for 18-22 minutes before sh'kia. As described below, when sh'kia comes in later, Mincha is scheduled slightly earlier, and when sh'kia comes in earlier, Mincha is scheduled slightly later.
- When sh'kia falls earlier than about 6:20, Mincha is called for 12-16 minutes before sh'kia. The goal here is to start as late as possible since people will have a hard time getting to shul so early.
- When sh'kia falls later than about 7:10, Mincha is called for 25-29 minutes before sh'kia, and when sh'kia falls later than about 7:30, Mincha is called for 32-36 minutes before sh'kia. The goal here is to start early enough to allow for a d'var halacha and to start Maariv as early as possible so that we can get home and start the Shabbos meal as early as possible. Also, when Shabbos is coming in that late, people don't generally have a difficult time getting to shul on time.
- When sh'kia is so late that Plag HaMincha falls out later than 6:10 pm, we switch to early davening, with Mincha before plag and Ma'ariv after plag and before sh'kia.
- Shabbat Mincha is ordinarily scheduled for 30-34 minutes before sh'kia. This allows enough time to complete Mincha and Shalosh Seudot (including z'mirot & divrei Torah) and daven Ma'ariv & Havdalah just after Tzet HaKochavim.
- The Shabbat candle-lighting and Havdalah times are posted on the site and calculated at 19 minutes before sh'kia and 43 minutes after sh'kia, respectively. The extra minute window added to these two times is a locally rabbinically enacted precaution in recognition that the correct sunset time actually deviates slightly across the Denver geographic area and from one source to another.
- During early davening (by plag), the Shabbat candle-lighting time is displayed as a range, from 2 minutes after plag until 19 minutes before sh'kia. One may not light Shabbat candles before Plag HaMincha; adding 2 minutes is a precaution, as explained above.
The daily davening times are fixed for Shacharit, but weekday Mincha (Sun - Thur) is automatically generated and posted Thursday mornings for the following week.
Disclaimer: The times are believed to be accurate to within 1-2 minutes, but as such are to be considered only approximations. No representation or warranty is provided as to the precision or correctness of the z'manim calculations. If you ever have any doubts about the times, it is always best to consult your friendly neighborhood halachic authority.
DO NOT RELY UPON THE SHABBOS Z'MANIM DOWN TO THE LAST MINUTE TO NOT BE MECHALEL SHABBOS!
