What is the best way to store Due Dates? - php

Question

I have an application that needs to store due dates. So if Bob in the UK creates a task and says it's due on Feb 20, I want it to show as Feb 20 on the Calendar regardless of timezones of other users.
Storing it as UTC as DATETIME in MySQL presents the problem that if Bob created the task at 1am Feb 20, then Jane in California would see the task as due Feb 19.
So my other thought is to store it as DATE but I couldn't find any literature on how DATE is affected by the TimeZone.
So my question is, if my app is PHP and my storage is MYSQL and I want to implement Calendars that only store dates and not date/time and I want events to show as a certain date globally, how should I go about it?
Aside from my particular needs, I'm also curious on how other people implement date specific events (do you just let the date be different on different users calendars?) - For example how does Google Calendar/Outlook handle "all day events"?

Answer 1

You can just store the date as a DATE field. Since you want all users to see the same date there's no need to worry about timezones or the like. I.e. storing 2014-10-11 in the column and then showing that value to users.

Answer 2

The safest way to do this is to store both the unix timestamp and the timezone of the job creator. Then, when displaying the date for other users, use that timezone for displaying the time:
$timestamp=1413027859;
$timezone='Australia/Sydney';
$dt=new DateTime();
$dt->setTimestamp($timestamp);
$dt->setTimezone(new DateTimeZone($timezone));
$day=$dt->format('Y-m-d');