Below is how to determine last modified date of a web page easily.
Several webpages do not list the last date they updated, modified or changed. But you can get the information of how to determine last modified date of a web page below.
Although this website will not give you an exact modified date, it will give you a general info. This website allows you to view history of a page, even if it’s offline. Go the the internet Archive and type in the Url you want to know.