DatePlus

gives the date n days after date.

DatePlus[date,{n,step}]

gives the date n calendar steps after date.

DatePlus[date,{{n₁,step₁},{n₂,step₂},…}]

gives a date offset by n_i steps of each specified size.

gives the date n days after the current date.

gives the date with the specified offset from the current date.

Details and Options

	DateObject[…]	date object
	{y,m,d}	year, month, day
	{y,m}	the first day of the specified month
	{y}	January 1 of the year y
	"string"	date as a string ("Jan. 1, 2000")
	{y,m,d,h,m,s}	precise time
	time	absolute time specification

Possible step sizes are calendar steps and day types "Year", "Quarter", "Month", "Week", "Day", "Hour", "Minute", "Second", "Weekday", "Weekend", Monday through Sunday, "EndOfMonth", and "BeginningOfMonth", "BusinessDay".
Offsets can also be specified using the Quantity framework.
{y,m,d} is taken to be equivalent to {y,m,d,0,0,0} etc.
DatePlus[date,offset] gives results in the same general format as date.
When date is a list, the result has the same length as date, possibly extended to include the smallest step in offset. »
When date is a string, the result is in the form specified by $DateStringFormat.
DatePlus takes the following options:

	CalendarType	"Gregorian"	calendar in which the dates have been specified
	HolidayCalendar	{"UnitedStates","Default"}	holiday schedule and subspecification for the business day and holiday computations