The standard way for switching from/to user_timezone and gmt

问题

I use php's date_default_timezone_set() and set it according to user's timezone field in the the user table. So with ease I can show date/time to users and get date/time from them.

But for storing date related values in database, I have to use the standard GMT timezone.

The question: What is the best or maybe the standard way for switching to/from user_timezone and GMT?

Do you suggest me to follow these steps when I want to insert or update a field in database?

1. Change the timezone using date_default_timezone_set('GMT');
2. Get the time using $inserttimestap = time(); or $inserttimestamp = mktime();
3. Change the timezone back to user default using: date_default_timezone_set($this->session->userdata('timezone'));

回答1:

There is absolutely no need to use date_default_timezone_set('GMT') because for converting to GMT, there is a special set of functions that the function names begin with 'gm':

• gmmktime() gets a timestamp in GMT timezone.
• gmdate() that gives a GMT date format.

• There is also gmstrftime() PHP manual

• Furthermore it's notable that the time() returns current timestamp only in GMT

来源：https://stackoverflow.com/questions/9099473/the-standard-way-for-switching-from-to-user-timezone-and-gmt