Showing the right time based on viewer's timezone

cadkins23

My goal: To output dates on pages that match the user's timezone.

Why I want this: Records are stored based using GMT. I don't want them thinking a message arrived for them at a different time than they actually arrived. Also the user shouldn't have to perform math to figure out when the message was received.

Recently I was told I should store the date and time in MySQL using the date/time data type so that I can later use MySQL's built in functions to manipulate the data. I can then convert the date to show to the viewer and convert back when storing.

This process has been giving me the most trouble so far.

I've researched for the best way to find the user's timezone and it looks like I'll have to use Javascript for that. I'm unaware how more professional or time tested scripts accomplish this.

The way that I came up with (which doesn't work all too well) is to instead of have PHP print the date to the screen, it hands the date over to Javascript in which Javascript is to get the viewer's timezone, make the change to the date and then Javascript write's the date to the screen.

One problem that I'm running into doing it this way is after the page has been sitting for a few minutes. If I hit refresh the dates jump forward several hours, if I hit refresh again they jump back, again and they'll jump forward. I can keep doing this and watch the hours seesaw back and forth each time I hit refresh. Another problem is that I have yet to figure out how to format a Javascript date so in the date/time field I have this:

Fri Jan 01 2010 22:04:31 GMT-0500 (Eastern Standard Time)

Another way may be to ask the logged in user upon registration what their timezone is and format the dates that way, although many of the more professional sites don't seem to do this and they seem to get the time's right.

I'm sure that many of you have faced the same dillemma, I'm curious how you went about solving this.

cadkins23

Perhaps my question can best be summarized like this:

How do most websites find the user's timezone?
Javascript?
A menu option during registration?
Determine from user's location?

halojoy

Most forums software use a personal setting in control panel.
You submit your offset from GMT.

This is my way.
Unix timestamp stores an integer representing GMT time, in seconds. In database.
function [man]time/man

Each user has one timeoffset +-hour from GMT

function [man]gmdate/man will return GMT-date.

Each hour offset is 3600 seconds.

Userdate = gmdate('format', timestamp + offset*3600)

We can allow users to select one personal 'format'.
Or, to make it more simple, use one standard 'format' for displaying date and time.

Because [man]date/man will convert Timestamp to local, servertime,
I do not use this function for international sites.
It is okay for a website with local visitors, with same time as server.

The above way will not solve the time for Guests, Visitors.
So, for those not Logged In, there has to be one choice of time for all.

cadkins23

I've decided to ask the user during registration what their time zone is. I'll store the dates and times of postings in a date/time type and use UTC and convert as needed. I'll probably end up using date_default_timezone_set(''); somewhere along the process. If anyone knows a better way, feel free to let me know 🙂

bradgrafelman

Just to throw out an alternative for those using PHP version >= 5.2.0:

$tz = new DateTimeZone('Europe/London');
$dt = new DateTime('now', $tz);
echo "Local time in London is: " . $dt->format('H:i:s \G\M\TP');

// output: Local time in London is: 00:33:18 GMT+00:00