How to determine one year from now in Javascript

You should use getFullYear() instead of getYear(). getYear() returns the actual year minus 1900 (and so is fairly useless).

Thus a date marking exactly one year from the present moment would be:

var oneYearFromNow = new Date();
oneYearFromNow.setFullYear(oneYearFromNow.getFullYear() + 1);

Note that the date will be adjusted if you do that on February 29.

Similarly, you can get a date that's a month from now via getMonth() and setMonth(). You don't have to worry about "rolling over" from the current year into the next year if you do it in December; the date will be adjusted automatically. Same goes for day-of-month via getDate() and setDate().

This will create a Date exactly one year in the future with just one line. First we get the fullYear from a new Date, increment it, set that as the year of a new Date. You might think we'd be done there, but if we stopped it would return a timestamp, not a Date object so we wrap the whole thing in a Date constructor.

new Date(new Date().setFullYear(new Date().getFullYear() + 1))