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

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

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+# 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)