query orders by date AND time in craft commerce
'&gt;= ' ~ dateFrom|date('c')


is correct to output the DateTime object as a string with the time (and timezone) included. If you don’t use the filter it’s output in the Y-m-d format by default.

So my recommendation would be to double check what dateFrom|date('c') actually outputs and to compare it with the dateOrdered values in the CP or database.