Using the =Date() Formula we will convert numbers run together as a vaild date readable by Google Sheets.
In this example my date text was YYYYMMDD and needed to convert it to a valid spreadsheet readable date like YYYY-MM-DD or 2016-01-01
Happy New Year BTW ;)
Our formula used in this sheet was =DATE(LEFT(C7,4),MID(C7,5,2),RIGHT(C7,2))
(where C7 is the cell of the data you will be converting.)