Year period management for moment.js. Requires the moment.js library. Default period is the standard US year divided into quarters.

moment.period.coffee

moment.fn.periodStartDates = [ 
  {month: 0, day: 1}
  {month: 3, day: 1}
  {month: 6, day: 1}
  {month: 9, day: 1}
]

moment.fn.period = ->
  period = Math.floor(this.month() / this.periodStartDates.length)
  start = moment(_.extend(this.periodStartDates[period], {year: this.year()}))
  end = moment(_.extend(this.periodStartDates[(period + 1) % this.periodStartDates.length], {year: this.year()})).subtract('millisecond', 1)                                                                        

  if start > this then start.subtract('year', 1) else if end < this then end.add('year', 1)

  return {start: start, end: end}

Requires underscore.

Line 9 should have Math.floor instead of Math.ceil.

this.month() returns a 0-based month index, and the periodStartDates array has a 0-based index

March (2) divided by this.periodStartDates.length (4) equals 0.5 and should be floored to 0 to be in the period that begins on January 1.

Ran into this bug in some old code we still have in production :-)

@awesomebob Good catch, thank you! This is super old :D