In the Bible, the concept of time, including days and months, is integral to the narrative and theological framework. The Hebrew calendar, which is primarily lunar, plays a significant role in the religious and cultural life of the Israelites, as outlined in the Scriptures.

Days:

The biblical account of creation in Genesis establishes the seven-day week, with six days of creation and the seventh day as a day of rest, known as the Sabbath. Genesis 2:2-3 states, "By the seventh day God had finished the work He had been doing; so on that day He rested from all His work. Then God blessed the seventh day and sanctified it, because on that day He rested from all the work of creation that He had accomplished."

The Sabbath is a recurring theme throughout the Bible, serving as a covenant sign between God and Israel (Exodus 31:16-17). It is a day set apart for rest and worship, reflecting God's rest after creation.

Months:

The Hebrew calendar consists of twelve months, with a thirteenth month added periodically to align with the solar year. The months are based on lunar cycles, beginning with the new moon. The Bible often refers to months by their ordinal number or by their Canaanite names, which were later replaced by Babylonian names after the exile.

1. Nisan (Abib): The first month of the Hebrew calendar, significant for the Passover festival. Exodus 12:2 declares, "This month is the beginning of months for you; it shall be the first month of your year."

2. Iyyar (Ziv): The second month, mentioned in 1 Kings 6:1 as the month when Solomon began building the temple.

3. Sivan: The third month, during which the Feast of Weeks (Pentecost) is celebrated (Exodus 34:22).

4. Tammuz: The fourth month, noted for the fast commemorating the breach of Jerusalem's walls (Zechariah 8:19).

5. Av: The fifth month, associated with the destruction of the First and Second Temples, observed with fasting and mourning.

6. Elul: The sixth month, a time of preparation for the High Holy Days.

7. Tishri (Ethanim): The seventh month, marked by significant festivals such as the Feast of Trumpets (Rosh Hashanah), the Day of Atonement (Yom Kippur), and the Feast of Tabernacles (Sukkot) (Leviticus 23).

8. Cheshvan (Bul): The eighth month, mentioned in 1 Kings 6:38 in relation to the completion of Solomon's temple.

9. Kislev: The ninth month, during which the festival of Hanukkah is celebrated, though not mentioned in the Hebrew Bible.

10. Tevet: The tenth month, noted for the fast commemorating the siege of Jerusalem (2 Kings 25:1).

11. Shevat: The eleventh month, mentioned in Zechariah 1:7.

12. Adar: The twelfth month, known for the celebration of Purim, as recorded in the Book of Esther.

The biblical calendar is not only a means of marking time but also serves as a theological tool, reminding the Israelites of God's acts in history and His covenantal relationship with them. The festivals and holy days are divinely appointed times for worship, reflection, and community gathering, reinforcing the rhythm of life centered around God's redemptive work.