Is it a valid way of comparing dates:
Calendar someCalendar1 = Calendar.getInstance(); // current date/time
someCalendar1.add(Calendar.DATE, -14);
Calendar some
It's valid, but you're slightly confused about someDate - Calendar.setTime takes a java.util.Date, which is just a wrapper around a long indicating the number of milliseconds since midnight Jan 1st 1970, UTC. It's not "in the format MM/dd/yyy" - that's a string representation, not a java.util.Date. If it happens to print something out in the format MM/dd/yyyy, that's just what Date.toString is doing for you - it's not inherently part of the format.
As an aside, I would personally recommend that you avoid java.util.Date and java.util.Calendar completely and use Joda Time instead. It's a much better API.