为从页面加载的javascript函数中获得的文本框赋值

Quick background: I am new to programming and have been using VisualStudio, ASP.NET, and C# for a couple months. I have no experience with JavaScript. I am trying to convert times from UTC to the time local to the browser viewing a page. After research I believe my best option for the various things I need to do is to detect the local offset from UTC on page load and then hold that information to use for local conversion and postback to the server. Quick background: I am new to programming and h