bootstrap datetimepicker today dd/MM/yyyy

As per the documentation, just set the format property.

See the configuration section for different ways of setting options. For example (using datetimepicker instead of datepicker):

$('.datetimepicker').datetimepicker({
    format: 'dd/mm/yyyy',
})

I would be wary of setting a specific format explicitly though - it would be better to honour the user's culture settings, unless you know for sure that all your users are happy to use the same format.