DateTime.addDays vs plusDays


The difference is that “add” will change the original object while “plus” will create a new instance without mutating the old one.
By using var dt =; dt.addDays(1) you can change the original instance by adding one day. By using dt.plusDays(1) you will get a new instance of DateTime by adding one day to the original instance. The same applies to hours, months and etc.


Also addDays (along with addHours, addMinutes, etc) is deprecated and should not be used.