DayMinusMonths Method

public Day MinusMonths(
	int numberOfMonths
)

Public Function MinusMonths ( 
	numberOfMonths As Integer
) As Day

Parameters

numberOfMonths  Int32

The number of months to subtract from this Day. Can be positive (to go backwards in time), zero, or negative (to go forwards in time).

Return Value

This will happily cross the borders between years, and it will always ensure that the returned result is a valid Day, unless it is outside the range allowed by Day (0001-01-01 to 9999-12-31 inclusive), in which case it will throw an OverflowException.

The DayOfMonth of the returned Day will be the same as that of this Day when possible, but sometimes it will have to be reduced, to fit within the constraints of the resulting month. For example:

• 2020-05-31 minus 1 month would give a result of 2020-04-30 (because April only has 30 days, 2020-04-31 would not be a valid date, so this will return 2020-04-30 instead).
• 2020-04-30 minus 2 months would give a result of 2020-02-29 (the last day in February 2020, which has 29 days instead of 28 because 2020 is a leap year).

However, the DayOfMonth will only change when absolutely necessary, for example:

• 2020-03-31 minus 2 months will give a result of 2020-01-31. It does not matter that February 2020 had only 29 days because we are subtracting 2 months, not 1.
• 2020-02-29 minus 48 months (i.e. 4 years) will give a result of 2016-02-29. 2020 and 2016 are both leap years, it does not matter that the years in between are not.

Day is immutable, so calling this method will not change this Day.

Reference