DateTime :: subtractYears - Subtract years from date value
The function subtracts a number of years from the current date and returns the new timestamp value.
Return value:  Time stamp ( odaba::DateTime & )
A time stamp combines date and time
Implementation details
odaba::DateTime &
DateTime  :: subtractYears ( int32 iYears )
The number of years passed in iYears is subtracted from the date value. Month and day remain unchanged, except for February 29th, which might be adjusted to February 28th.
- iYears
 - Year number
Number of years or year number. 

