mixed dates to harmonize

I have a spreadsheet with mixed date formats -

11-Aug-2016
09MAR2017 15:22
09MAR2017 15:22
05-Aug-2016
28-Jul-2016
09MAR2017 15:22
20APR2017 08:25
3/20/2017 9:50
03/01/16
04/12/16

Thought by using Format > Date I can harmonize all different formats into one. It does not seem to work.

A google search suggests I need to write a VBA. Is it the only way to harmonize the dates ?

If I copy/paste the above values then they are all recognized as dates and I can indeed format them all consistently.

In your case, I wonder if some / all of the dates are actually text that look like dates rather than numbers representing dates?

What do you see if you do isnumber() on each of the dates? If some/all return FALSE you might try timevalue() to convert to a proper date, then you can format as you wish.

Thanks !
I think you meant datevalue
(timevalue gives me 1/0/1900)