Short answers, pulled from the story.
The concept of a null value existed in administrative contexts in ancient Egypt around the 4th millennium BC. Scribes used the hieroglyph nfr to indicate when the amount of food received equaled the amount disbursed. This usage suggests that the concept of a null value existed in administrative contexts long before it was formalized in mathematics.
The mathematician Brahmagupta established rules for arithmetic operations involving zero in the 7th century. He wrote the Brahmasputha Siddhanta and stated that the sum of zero with itself is zero and that zero divided by a positive number is zero. Although his rule for division by zero was incorrect, he was the first to treat zero as a number with its own properties.
The symbol for zero evolved into a small circle by the 9th century. This evolution is seen in the inscription at the Chaturbhuj Temple in Gwalior, India, dated 876 AD. The symbol had previously been a black dot in the Bakhshali manuscript dating from the 7th to 11th centuries.
The Italian mathematician Leonardo of Pisa, known as Fibonacci, popularized the system in 1202. In his book Liber Abaci, Fibonacci described the nine Indian digits and the sign 0, arguing that the method was superior to the cumbersome Roman numerals. The decimal notation gradually displaced the abacus and Roman numerals, becoming the standard for European mathematics by the 16th century.
The Unix epoch begins at midnight on the 1st of January 1970. This date marks the zero timestamp for computer systems. The number zero also plays a critical role in database management, where a null value indicates the absence of data, distinct from zero itself.