如何将结束日期与引导程序中的开始日期进行比较，以确保结束日期大于开始日期

I am new to coding world. I am making a webpage using bootstrap to take in 'Start date' and 'End date' in the page. But the problem is I don't know how to make end date always greater than start date. I have pasted the code here which I got from the internet. Any help will be appreciatedI am new to coding world. I am making a webpage