When using Google Spreadsheet today, I noticed that when entering a date as a simple number sequence (e.g., 151127), and choosing date as format, it ended up being a completely different date than the one intended (i.e. not 2015-11-27, but rather 2313-10-08).
After a bit of tinkering, I realized that each unit represented one (1) day from 1899-12-30, meaning that 151127 (onehundred-and-fifty-one-thousand-onehundred-and-twentyseven) is that many days from 1899-12-30.
My question is:
Is there a specific reason for using days as unit for this kind of date entry and, if so, what is it?