Text dating numbers
You can make the change for an entire worksheet by clicking the small box above 1 and to the left of A in the top-left corner, or by pressing Ctrl-A or Command-A to select all the sheet's cells.
Then right-click any cell, choose Format Cells, and select Text in the left pane under the Number tab.
Here's how I eventually solved the problem: I discovered from my troubleshooting that Numbers uses your computer's region setting to determine the anticipated input date format.
In my case, my region under System Preferences - Language & Region is set for Canada.
When you exit the cell, the apostrophe vanishes and the numbers stay numbers, formatted as text. I have a CSV file which contains numerous dates in the format MM/DD/YYYY.I need to convert these dates into datetime format for insertion into a My SQL table. Choose the 2014-01-23 style for date and for the time.When I tried to convert it in Numbers 3.5 by simply changing the format of the cell the change was rejected and the cell format defaulted back to "Automatic".
So I tried using the DATEVALUE formula to convert it and again I was presented with an error.I have a slight problem, I have a date format coming from php my admin, which is: 1975-09-31 - this is in the format YYYY-MM-DD.