Codechange: Add base() method to StrongType to allow access to the base type without casting. (#11445)

This removes the ability to explicitly cast to the base type, but the requirement
to use .base() means the conversion is still explicit.

Fix 646a7e62: recalc_time was not scaled properly (#10901)

This caused "runtime" to underflow or, if you are lucky, hit an
assert in ScaleToMonthly when it hits zero. But mostly underflow.