We can check that a given variable is a date object or not. To check this, we have various approaches. Let check one by one.

Solution 1:

It will work for most cases, but it will fail on multi-frame DOM environments

(myvar instanceof Date) && !isNaN(myvar) // return true or false

• Checks if object is actually a Date and not something that looks like one.
• isNaN Ensures the Date is not an Invalid Date

Solution 2:

typeof myvar.getMonth === 'function'

Check string is date or not in JavaScript 

Solution 3:

If you need to support iframes and different contexts, you can use the accepted answer but add an extra check to identify invalid dates

(myvar && Object.prototype.toString.call(myvar) === '[object Date]' && !isNaN(myvar)) 
// returntrue or false

1. myvar checks whether the parameter was not a falsy value (undefined, null, 0, "", etc..)
2. Object.prototype.toString.call(myvar) returns a native string representation of the given object type – In our case "[object Date]". Because date.toString() overrides its parent method, we need to .call or .apply the method from Object.prototype directly which ..
   • Bypasses user-defined object type with the same constructor name (e.g.: “Date”)
   • Works across different JS contexts (e.g. iframes) in contrast to instanceof or Date.prototype.isPrototypeOf.
3. !isNaN(myvar) finally checks whether the value was not an Invalid Date.

Source : Stackoverflow