Although zero has been used widely for centuries, zero is in fact a recent invention. Different civilizations had used the idea of zero. The Sumerians were the first people in the world to use the idea of zero. Around 4,000 to 5,000 years ago, the Sumerians developed a positional system where different positions meant different symbols. In that system, the Sumerians used diagonal lines as a placeholder for zero.
On this ancient stone tablet from the Sumerian city-state Sumer, a pair of diagonal parallel lines were used to denote where there was no number. It had later changed to a pair of slanted wedges similar to the Babylonian way.
(Source-The Internet Archives)
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Around 350 AD, the Mayans developed zero as a placeholder and used it in their calendar systems. Even though the Mayans were skilled mathematicians, they were never able to use zero in mathematics. Even then, it is still remarkable that they invented an idea of zero fully from scratch. Due to religious intolerance, a lot of Mayan work had been destroyed, so it is still a mystery of how the Mayans had thought of zero.
"The second appearance of zero occurred independently in the New World, in Mayan culture, likely in the first few centuries A.D. That, I suppose, is the most striking example of the zero being devised wholly from scratch."
~ Robert Kaplan
(Author of the book, "The Nothing That Is: A Natural History of Zero")
This is the Base-20 system which was employed by the Mayans. In the system, zero was represented as a shell.
(Source-Texas A&M University
This is the La Majorra Stela 1 found in Veracruz, Mexico. The discovery of this text made possible the decipherment of the epi-Olmec writing system in 1993.
(Source-Science Magazine)