if dtpicker1.year-dtpicker2.year=1 then
month1=12-dtpicker2.month
summonth=dtpicker1.month+month1
endif
if dtpicker1.year-dtpicker2.year>1 then
month2=12*(dtpicker1.year-dtpicker2.year-1)
month1=12-dtpicker2.month
summonth=dtpicker1.month+month1+month2
endif