In-service date = 15.01.09
Useful life = 6.5 months
Expiry Date Calculation
Date for 6 months = 14.06.2009
Date for 0.5 months, = Add 15 days (30 * 0.5)
Therefore the Expiry Date = 29.06.2009.
Note that in the above calculation months are considered as having 30 days.