Add Create Future And Past Dates From Today as a javascript til

README.md

@@ -9,7 +9,7 @@ and pairing with smart people at Hashrocket.
 
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-_969 TILs and counting..._
+_970 TILs and counting..._
 
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@@ -324,6 +324,7 @@ _969 TILs and counting..._
 - [Create An Array Containing 1 To N](javascript/create-an-array-containing-1-to-n.md)
 - [Create An Object With No Properties](javascript/create-an-object-with-no-properties.md)
 - [Create Bootstrapped Apps With Yarn](javascript/create-bootstrapped-apps-with-yarn.md)
+- [Create Future And Past Dates From Today](javascript/create-future-and-past-dates-from-today.md)
 - [Custom Type Checking Error Messages With Yup](javascript/custom-type-checking-error-messages-with-yup.md)
 - [Default And Named Exports From The Same Module](javascript/default-and-named-exports-from-the-same-module.md)
 - [Define A Custom Jest Matcher](javascript/define-a-custom-jest-matcher.md)

javascript/create-future-and-past-dates-from-today.md

@@ -0,0 +1,34 @@
+# Create Future And Past Dates From Today
+
+JavaScript's built-in
+[`Date`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date)
+object can be frustrating to work with at times.  It does, however, lend itself
+nicely to some date math. You have to familiarize yourself with some of the API
+and then it is a matter of addition and subtraction.
+
+Here is today:
+
+```javascript
+const today = new Date();
+// Tue Dec 01 2020 ...
+```
+
+Let's make a copy of today and send it 30 days into the future:
+
+```javascript
+const future = new Date(today);
+future.setDate(future.getDate() + 30);
+future
+// Thu Dec 31 2020 ...
+```
+
+Or we could jump back a few years:
+
+```javascript
+const past = new Date(today);
+past.setFullYear(past.getFullYear() - 4);
+past
+// Thu Dec 01 2016 ...
+```
+
+[source](https://stackoverflow.com/questions/7908098/javascript-set-date-30-days-from-now/7908122#7908122)