Some early calendars developed by the Chinese Egyptians and Hebrews were based on the cycles of the blank

Lunar.

Explanation:

Some early calendars developed by the Chinese, Egyptians and Hebrews were based on the cycles of the moon because the cycles of the moon provides precise and accurate time. The formation of calendar by the ancient Egyptians also discovered the lunar year and then they were able to divided the year into seasons, months, days and hours. The moon changes its shape shows that the month is starts and ends.

radioactive dating, also known as  radioisotope dating  is a process that in  estimating the approximate  age  of  rocks. these data can be analyzed from  the studies dealing with the  decay of the radioactive elements that are present in these rocks. in nature, there are a few types of materials or atoms which are quite unstable and they spontaneously decay or breakdown to form other kinds of atoms.

wait history, who want to talk about history, boring.