You asked

how did israelites calculate the start and end of a sabbath day without clocks?

Adds the setting and its conversation across both testaments.

Nehemiah 13:19

“It happened that when the gates of Jerusalem began to be dark before the Sabbath, I commanded that the doors should be shut, and commanded that they should not be opened until after the Sabbath: and some of my servants set over the gates, that no burden should be brought in on the Sabbath day.”

This verse is from the book of Nehemiah, written around the 5th century BCE. Nehemiah, a Jewish leader returning from exile, is describing his efforts to restore Jerusalem and encourage his people to live according to God's covenant, including the proper observance of the Sabbath.

What practical steps do we take in our lives to mark transitions and dedicate time to what we value?

Then — the setting

In ancient Israel, timekeeping was largely observational, based on the sun's position. The day was understood to begin at sunset. Therefore, the Sabbath began at sunset on Friday and ended at sunset on Saturday. 'When the gates of Jerusalem began to be dark before the Sabbath' refers to the twilight period, the observable dimming of light as the sun descended, signalling the imminent start of the Sabbath. This required careful observation of the natural light and sky, rather than precise clock times.

Across the Testaments

The Old Testament explicitly establishes the Sabbath as a day of rest, often referring to it as beginning in the evening (e.g., Leviticus 23:32, though this specifically refers to Yom Kippur, the principle of 'evening to evening' was applied to the weekly Sabbath). The New Testament narratives confirm this practice; for example, the women waited until 'the Sabbath was past' to buy spices to anoint Jesus (Mark 16:1), and people brought the sick to Jesus 'when the sun had set' on the Sabbath (Mark 1:32), indicating the Sabbath's conclusion. Both testaments operate within the same understanding of a day running from sunset to sunset.

Keep thinking

Read alongside it

Leviticus 23:32
This passage specifies that the Sabbath (specifically Yom Kippur, but applied to weekly Sabbath) runs from 'evening to evening'.
Mark 1:32
This New Testament passage illustrates the common practice of waiting until 'when the sun had set' to bring the sick to Jesus, indicating the end of the Sabbath.

Ask your own follow-up