I have some cells in the format 15/05/15. Here is an example. These are dates, but as I copied them into Google Spreadsheets, they are apparently treated as strings. How do I convert them into date objects, preferably in the format 2015-05-15?

Clearly I should be choosing Format->Number and then a date format, choosing MM/dd/YY if needed to pin it down. I might then re-select and choose another format like the YYY-MM-dd that I need. But this does nothing.

(Actually, in some cases I got this sort of thing to work and in some cases I did not. I am not sure what makes the difference. Maybe ambiguous strings?)

How do I convert the dates?

I have some cells in the format 15/05/15. Here is an example. These are dates, but as I copied them into Google Spreadsheets, they are apparently treated as strings. How do I convert them into date objects, preferably in the format 2015-05-15?

Clearly I should be choosing Format->Number and then a date format, choosing MM/dd/YY if needed to pin it down. I might then re-select and choose another format like the YY-MM-dd that I need. But this does nothing.

(Actually, in some cases I got this sort of thing to work and in some cases I did not. I am not sure what makes the difference. Maybe ambiguous strings?)

How do I convert the dates?