I have a string of number in the following format: 2012.07.11
How can I convert this into a date format like you have above?

=DATE(LEFT(A1,4),MID(A1,5,2),RIGHT(A1,2))

Where A1 contains your date string.

P.s. Its not a good idea to piggyback your question on another thread. To avoid confusion I've moved your post to its own thread.

You "might" have success if you just highlight the cells in question, press CTRL-H (replace) and do a search for period and replace them with slashes.

2012-07-30_1747 - JerryBeaucaire's library