Quantities should not be printed directly because intermediate steps lead to definition of new units which are not a priori defined in the system: in this case the unit is of dimension `time` and of magnitude `0.03` so it is not a second; rather it is `0.03 s` since we use a system for which the reference time unit is the second.
For this reason at the end I'm doing an explicit conversion to get the result in days (but I couldhave asked for the result in seconds).
I started by using automatic conversions, but it was giving unreliable results, so after discussions with other people from sympy I decided to remove all magic conversions and let the user asks explictly what he wants at the end.