From Xojo Documentation

Property (As Integer )
aXojo.Core.DateInterval.Months = newIntegerValue
IntegerValue = aXojo.Core.DateInterval.Months

Supported for all project types and targets.

The number of months in the interval.

Sample Code

Get a date two months from today:

Dim di As New Xojo.Core.DateInterval
di.Months = 2 // 2 months

// Get date two months from today
Dim d2 As Xojo.Core.Date = Xojo.Core.Date.Now + di