Add New Dates Can Take Out Of Bounds Values as a javascript til

README.md

@@ -10,7 +10,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 For a steady stream of TILs from a variety of rocketeers, checkout
 [til.hashrocket.com](https://til.hashrocket.com/).
 
-_617 TILs and counting..._
+_618 TILs and counting..._
 
 ---
 
@@ -233,6 +233,7 @@ _617 TILs and counting..._
 - [Install The Latest Version Of Node With Nvm](javascript/install-the-latest-version-of-node-with-nvm.md)
 - [ISO-8601 Formatted Dates Are Interpreted As UTC](javascript/iso-8601-formatted-dates-are-interpreted-as-utc.md)
 - [Matching Multiple Values In A Switch Statement](javascript/matching-multiple-values-in-a-switch-statement.md)
+- [New Dates Can Take Out Of Bounds Values](javascript/new-dates-can-take-out-of-bounds-values.md)
 - [Numbers Are Empty](javascript/numbers-are-empty.md)
 - [Object Initialization With Shorthand Property Names](javascript/object-initialization-with-shorthand-property-names.md)
 - [Random Cannot Be Seeded](javascript/random-cannot-be-seeded.md)

javascript/new-dates-can-take-out-of-bounds-values.md

@@ -0,0 +1,36 @@
+# New Dates Can Take Out Of Bounds Values
+
+You can create a new date by feeding it arguments for _year_, _month_, and
+_day_.
+
+```javascript
+> new Date(2017, 11, 31)
+Sun Dec 31 2017 00:00:00 GMT-0600 (CST)
+```
+
+What happens if we push the _day_ value out of bounds?
+
+```javascript
+> new Date(2017, 11, 32)
+Mon Jan 01 2018 00:00:00 GMT-0600 (CST)
+```
+
+It rolls over to the next month.
+
+Does the same happen when we push the _month_ value out of bounds?
+
+```javascript
+> new Date(2017, 12, 31)
+Wed Jan 31 2018 00:00:00 GMT-0600 (CST)
+```
+
+Yep.
+
+What about negative values?
+
+```javascript
+> new Date(2018, -1, 31)
+Sun Dec 31 2017 00:00:00 GMT-0600 (CST)
+```
+
+It rolls the month, and consequently the year, back.