Align year selector to use zero indexed months

[duckboy81]

When using a year selector, the datepicker will return February of the selected year due to the fact that the JavaScript Date object's month value is zero index based. Updating the value passed here will direct the select_date function to pass the correct month value to the Date object.

**Example**
Selected year: 2018
Expected Date obj value: Mon Jan 01 2018 12:00:00 GMT+0000
Actual Date obj value: Thu Feb 01 2018 12:00:00 GMT+0000

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date

[stefangabos]

Thank you!