Defined time-periods constants for Javascript, in milliseconds. Exposed as functions to make mis-typing fail noisily, rather than manifesting as NaNs in your data.

var periods = require("periods");

var twentyFourHoursLater = Date.now() + periods.day();

var week = periods.week;

var durations = [1,2,3];
var weekDurations = durations.map(week);

Works in browser too.

Each method has a plural defined. e.g seconds(), monthsRough()

n * 1000

n * 60 * second

n * 60 * minute

n * 24 * hour

n * 7 * day

n * 4.3 * week

n * 365.25 * day