יד יוסף: What Time is It?

בס"ד

When G-d created the celestial objects he decreed that they should be for signs, seasons, days, and years. The rising of the sun creates a daily pattern. Counting seven days is a week. The new moon starts the month. The mean tropical year is approximately 365 days, 5 hours, 48 minutes, 45 seconds. This is a lot to count plus it involves calculations. The constellations of the Zodiac do provide a very usable guide. Variants of a sundial can be used like the angels in announcing the birth of a son to Sarah. Rashi comments that they put a mark on the wall and said that when the sun reaches this point in one year, Sarah will give birth. The seasons are aligned with the Zodiac, even though they do change over thousands of years. The appearance of the bright star Sirius coincides with the rising of the Nile River and signaled ancient Egypt that the time to plant had arrived. Abraham saw the planet Jupiter as an omen for his life’s adventures.

The moon is important to Jewish religious thought. The new moon starts the new month. When the Temple stood special offerings were made in it's honor. Now it is honored through special prayers. It's onset is formally announced in synagogue as part of the liturgy. After the new moon appears it is viewed and blessed by the congregation. In the blessing the concept of renewal is stressed because the moon waxes and wanes.This is followed with communal singing and dancing. The Jewish people are compared to the moon because at times it seems like they don't exist and other times it is as if they light up the night time sky.

Sunset is important because it is used to determine the start and the end of Shabbat and holidays. In addition sunrise, noon, and even midnight are used to set the times of prayer. The idea is that time and punctuality are important and that the tools available should be used for assistance.

It’s possible to estimate the time based on the position of the sun in the sky. Most people, though, wouldn't bother to figure it out and it doesn’t work on a cloudy day. The position of the polar constellations can be used to determine the time of night but they have similar problems. Sunrise and sunset are pretty clear but they change.

The idea is that knowing the time is useful and often essential. G-d gave man the luminaries as tools, however man has the ability to make advancements on them. A sundial is better than judging from the position of the sun and the stars. A clock is better especially if it has an alarm. A computer with many alarm clocks and a calendar with notifications is cutting edge technology.

This is implied in Isaiah 60:19, “The sun will no more be your light by day, nor will the brightness of the moon shine on you, for the LORD will be your everlasting light, and your God will be your glory”. Rashi: You shall no longer have - You shall not require the light of the sun.