Hello Bhupendra, 

For clarification purposes related to this issue, my interpretation was that you are entering into a date field in a model and then using your browser's "page back" button in order to navigate backwards. The date widget will still persist within the DB until you use your mouse to click outside of the box's range. (See attachment below) 

I have tested in a demo database, and it looks like this behavior is currently a bug within versions 18-18.3, and it is not present in any of the older versions. Are you currently working within version 18 or newer? 

In terms of best practice, it is never advisable to navigate using your browser's advance or back buttons and instead to navigate using Odoo's internal tools such as 1) the menu bar & 2) the breadcrumb menu (depicted below) as sometimes using the browsers buttons causes strange use cases such as this. 

An internal bug ticket has already been created and is hopefully in the works to create this behavior. But your input is also valued. If you have your database still exhibiting this behavior, feel free to create a ticket at help.odoo.com so that our internal team can take a look at it. 

If this is not the behavior you are describing, let me know, and I can see if I can look into it.