Fixing extra zero being added in setValue()

fe710b582 adds zeros being added to values of the DateSelectorField,
but on cases where setValue() is being called, an extra zero is being
added to the value, so instead of 1980-01-01 it'll come out as
1980-001-001 instead.
Merge pull request #4 from halkyon/setvalue_regression

Fixing extra zero being added in setValue()