time date formatting issues

That date/time format looks fine, it's basically kind of the standard format.

How is Excel not recognising it?

Are you 'telling' Excel to treat that column as a date/time?

I was actually thinking more of when you are importing the data.

How are you importing?

PS You can check if Excel is recognising the 'date' using ISNUMBER, if that returns TRUE it is a date, FALSE it isn't

PPS Might be worth checking for trailing/leading/errant spaces etc

Maybe the imported data has spaces before and after the data and it is possible that the space between the date and time is not really a space but another character that looks like a space.

Select the space in the date/time string and copy it. Paste that into say M1. In N1 enter =CODE(M1) If the code isn't 32 then the space isn't a space.

If the date and time are entered in column A enter this in column B and copy down the length of your data.

Formula:

=TRIM(SUBSTITUTE(A1,CHAR(160)," "))*1

If the code in N1 isn't 160, use that number in the CHAR() function. Format the date and time the way that you want (dd/mm/yyyy hh:mm:ss)

The above will trim off any leading or trailing spaces and "fix" any strange spaces if you found a strange code for the space. A normal space between the date and time will be left alone.

I multiplied the date by 1 then copied the result back into the date column formatted as dd/mm/yyyy hh:mm:ss.

Workbook with calculation enclosed.