Mathematical tablet from Uruk, late third or early second century BC, containing one of the earliest known instances of the Babylonian zero; Louvre, AO 6484 side B.

On the line 14 of the tablet we can read:

The learned men of Babylon had no concept of zero around 1200 BC [as on the tablets from Uruk]. Despite their strictly positional nature and their sexagesimal base, learned Babylonian numerals remained decimal and additive within each order of magnitude. This naturally created many ambiguous expressions and was thus the source of many errors. In any numerical system using the rule of position, there comes a point where a special sign is needed to represent units that are missing from the number to be represented. To overcame this difficulty, Babylonian scribes sometimes left a blank space in the position where there was no unit of a given order of magnitude [as on the tablets from Suza, 1800-1700 BC].

At some point, probably prior to the arrival of the Seleucid Turks in 311 BC, Babylonian astronomers and mathematicians devised a true zero, to indicate the absence of units of a given order of magnitude. They began to use, instead of a blank space, an actual sign wherever there was a missing order of the powers of 60, and the sign they used was a variant of the old ‘separator’ sign [which was used in literary text]:

Georges Ifrah: The universal history of numbers, Transl. from 1981 French ed., J. Wiley & Sons, New York, 1998.

True, zero is not an easy concept. Zero is not nothing, it is a numeral which is essential in every positional numerical system built upon orders of magnitude. Unfortunately, in US it remains a grueling concept even today. You can see numbers smaller than 1 written without zero in front of a decimal point, like zero is nothing, for example

.714  instead of   0.714

and this is used not only in general writings but in science and engineering also. Nevertheless, zero is not a very modern concept: it was less peculiar to the ancient civilizations than it is to Americans today.

If it is true that Babylonians introduced a full-fledged zero somewhere between the sixth and third centuries BC (read: if we don’t find tablets between the twelfth and sixth centuries BC showing otherwise), then Babylonians needed at least six centuries to put the zero symbol into the empty numeral space. Thus, can we expect an American zero in front of a decimal point before the year 2092 (=1492+600)?