tiny.cc/jmt-clock

JMT Clock and Molad Calculator with Changing Skin

         
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NIGHT SKIN DAY SKIN
FacesJ-s.jpg
The red dots mark "parts." (1 part = 1/18 minute = 3 and 1/3 seconds.)

     JMT Clock     

This page displays the Auto Clock.   Its skin will change at 12-hour intervals. Use the "Test" button to preview what happens during those changes. To exit testing mode, press the "Test" button again while the 'wrong' skin is showing.

This is a 24-hour clock, but with a 12-hour dial. It differentiates between am and pm times by changing its skin every twelve hours. At mean sunrise, which is 6 am (06:00), it switches to the day skin, and at mean sunset, which is 6 pm (18:00), it switches to the night skin. The two times just mentioned are Civil Time (CT).

This clock shows both Civil Time (CT) and Jewish Mean Time (JMT). For CT, ignore the numbers and just note the hand positions. For JMT, note the numbers.

JMT = CT + 6 hours, e.g. Friday, 18:00, CT = Saturday, 00:00, JMT, because a Jewish calendar day begins, not at midnight, but six hours earlier at mean sunset, which, therefore, is zero hours, JMT. And in JMT, the mean times of midnight, sunrise and noon are 06:00, 12:00 and 18:00.

Note: For this site to work properly, your browser must support the HTML5 Canvas object and have javascript enabled (which is recommended and is quite safe).

I could use occasional advice on javascript. If anyone is interested in helping me with this project, please see the project page to get in touch.

 

Scroll down to see the Molad Calculator.

 

 

           
Year, Month Molad: JT = CT     1m
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L = 4 weeks, 1 day, 12 hrs, 44 min, 1 part
אין בין מולד ומולד אלא יום א', י"ב שעות, ותשצ"ג חלקים (p‏ 793).

Molad Calculator

This (stopped) clock is a graphical time calculator for calculating moladot (calendric, mean New Moons) and to help you understand them. (This is unfinished.)

The fixed interval (L) between moladot, and hence the calendar's mean month length, may be called a calendric lunation. L = 29.5 days, 44 minutes and 1 part, which very closely approximates the Moon's mean synodic period (a full cycle of lunar phases).

Moladot are given as weekday w, time t, where w = 1 to 7 for Sunday to Saturday, and t is in 24-hour notation. They are given in two forms:
w, hh:pppp, JMT (0 to 23 hrs and 0 to 1079 p), and
w, hh:mm:pp, CT (0 to 23 hrs, 0 to 59 min, 0 to 17 p).
(p = parts. 1 hour = 1080 p, and 1 minute = 18 p.)

Molad Tohu is the calendar's epoch, the molad of month 1 of year 1.

Current Molad is this month's molad, if the Jewish date is before the 20th, or next month's molad if it is after the 19th. (For now, it just shows one preset molad.)

Use the + or - button to go forward or backward in the calendar by a selected interval, which you can change with the Interval button. It can be: 1 month, 1 year, or 1, 13, 100, or 1000 Metonic cycles. A Metonic cycle has 12 common years and 7 leap years (= 19✕12+7 = 235 months).