Problem with Numbers and dates in El Cap...

Hi,
I'm running the GM of El Capitan on our work 2012 rMBP. Part of my job entails working with inventories to upload the most recent changes from one channel to another.

To achieve this I've been opening a .csv in numbers, selecting a column populated with dates, then going to the 'Cells' inspector and formatting the column with the appropriate date/time values which allowed me to sort the column by ascending/descending. This worked perfectly in Yosemite and before (in fact, when I first encountered this issue on the PB I rebooted into the Yo partition to double check) but for some reason has stopped in El Cap; Numbers simply does not recognise the column as a list of dates and times and thus it is unsortable.

I could download Open Office and get round it that way, but I really liked the simplicity of Numbers. I did read some suggestion that this can be caused when there's a discrepancy between how the dates are formatted and how the computer is set to format them, so I double checked the the computer was set to UK-style dates. It is, so that shouldn't be an issue. One other thing: I used to be able to choose hour-minute-second GMT on the 'Time' drop down list but that seems to have gone as well.

Does anyone have a suggestion for fixing this? I checked on an older raw .csv that I was able to process perfectly some months ago and saw the same problem above, so it's not just that there's an issue with the file I've been trying to work with.

Many thanks in advance!

 

Worked perfectly! Just as expected. On the same computer (different partition), using the same file and very probably the same version of numbers.