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First thing's first: my spreadsheet's locale is properly set to UK:
If I paste in the following date:
Then click Format > Number > Date time
Nothing changes. I also can't seem to sort by date.
This has now been resolved by Google Spreadsheets. Pasting in the date:
And clicking Format > Number > Date time now immediately turns the cell into a date time cell (you can see this as it adds seconds).
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