I have a HTML form which has a date and time field. I assume that when a user enters a date/time, they are doing so in their local time, but when I store it in the database, I need it in UTC, and then when displaying it I need to adjust it to the viewers time.
Can I know the clients timezone from the server (I am using PHP and Apache, but may use IIS in the future, so would rather not rely on Apache-only behavior if possible)? Or can I do UTC <-> Local conversions on the client in Javascript?
Example:
A user in UTC+1 timezone submits 2012-10-18 01:30. This should get stored as the timestamp of 2012-10-18 00:30:00 (whatever that is). Then, if a client at UTC-5 with local DST views the record, they should see 2012-10-17 20:30.
<html>
<head>
<script>
function test()
{
var d = new Date(2012, 6, 13, 12, 0, 0, 0);
console.log(d);
var hours = d.getUTCHours();
console.log(hours);
}
</script>
</head>
<body>
<input type="button" onclick="test()" value="test"/>
</body>
</html>
You input d as local time, and get UTC time by using getUTCHours(), getUTCDates(), etc... Then send UTC time back to server.