Move this date earlier by the specified (signed) number of days.
Assign to this object the value that is earlier by the specified (signed) numDays from its current value, and return a reference providing modifiable access to this object. The behavior is undefined unless the resulting value falls within the range of dates supported by this class (see isValidYearMonthDay). Note that numDays may be negative.
reference providing modifiable access to this object
| Name | Description |
|---|---|
| numDays | signed number of days to subtract |