I know this has been asked here several times, but the 'by-the-book' custom way to do it still remains unclear to me.
I'm designing an app which requires knowing the exact user's local-time. I got really confused while researching this:
Most experienced SO users recommend just asking the user for her timezone. Others recommend the Javascript timezone offset method. Another approach is to use geolocation.
Facebook posts and Gmail mails, for example, shows the exact local time, regarding DST and everything. I was never asked for my timezone by these applications. Which method might they use?
Or, among the above and other methods, which method is the custom, 'by the book' way to be able to use and store the user's local-time?