As they continue their studies, it will not be necessary to know, for instance, exactly what year King David was born. One reason for possible confusion will be that the books of the Bible, as presented in most English translations, are not in strict chronological order, either according to the time they were written, or according to the events they describe. It is a collection of 66 smaller books, combined under one cover. These books were written by a wide variety of authors, over a period of over 1000 years. Some events are described by more than one author.
Some authors cover a much longer time period than others.
Because these lessons are reaching out to a varied audience, it is hoped that all will understand the need to sometimes start with very basic principles and build the more complex concepts on those. If you have been a Bible student, or world history student, for some time, you may be able to quickly read over these foundational materials. However, even those quite familiar with the material may find it helpful to consider some of the simple principles a little more carefully if they plan to share the concepts with newer students. Sometimes when we move on to more complex information in our own studies, we forget how to communicate the simpler topics to others. Although this method of describing time is almost universal now, throughout much of history each civilization had its own unique method of calculating and referring to historical time.