I\'m pretty sure this worked properly in previous versions of Excel
Test File:
d/mm/yyyy hh:mm:ss
5/12/1999 6:01:12
30/11/2001 5:00:00
It seems like this might be the same issue addressed in this thread:
Opening CSV files in Excel 2016
CSV files are Character Separated Value files, not Comma separated. For more than half the world the separator character is semicolon (;), not a comma (,)
Excel 2016 properly respects your Windows regional settings, and uses the specified "List separator" character
One solution is to change your regional settings for the "List separator" attribute to the character you want Excel to default to using, e.g. a comma (,)
This can be changed in:
Control Panel / Region / Additional Settings / List separator: