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marcparillo

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MySQL + PHP Timestamp advice


What's the best method for recording times in a MySQL database?  For years, I've used unix timestamps (i.e. 1323092395) but when I need to take DST into account, it becomes an issue.

For example, Client A wants an e-mail sent to her at 5am every day.  The time is recorded as a unix timestamp in my database.  When DST starts, the server time is automatically adjusted back an hour, and suddenly, Client A starts receiving e-mails at 4am because the unix timestamp is a relative number, not a fixed point in time such as a UTC timestamp.

I've read Ray Paseur's great article from EE about Handling Date and Time in PHP and MySQL, but those solutions are all PHP based.  I would like to do the time adjustments on the MySQL end, so I don't have to perform a time function on every record in the DB.

Should I use UTC, RFC 2822?  If I use those formats, would I be able to perform a MySQL query that takes into account the time change?

Thank you,
marc


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effx
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Could you not work out the offset on the unix time?
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marcparillo

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Can you give me an example of what you mean?  
YOURUNIXTIME - (60*60*2)

I think thats right for minus 2 hours
I understand your suggestion, but I'm looking for something more durable, I guess.  I don't want to be changing my code every time DST comes and goes.  I was hoping there was a way to maintain the actual time in MySQL.  I'm thinking using DATETIME may be the solution. I'll keep looking around.
"... perform a time function on every record in the DB"

Why not?  MySQL cannot send the email messages, so you will probably be needing to use PHP for something.  I would just do this the easy way.  Store the client's timezone information and adjust the time zones as needed for each client.
Hi Ray,

Thanks for responding.  If I had a database of several hundred people, all of whom need an e-mail sent a different times of the day, I was trying to avoid looping through the DB every minute.  I would just like the DB to return records that match the current hour and minute of the server, depending on how the timestamp was recorded.  Something like:

... if storing a unix timestamp
SELECT first, last, email from EmailTable WHERE DATE_FORMAT(from_unixtime(emailtime),'%H:i%')=09:00;

... if storing the time like YYYY-MM-DD HH:II:SS
SELECT first, last, email from EmailTable WHERE HOUR(emailtime)=9 AND MINUTE(emailtime)=0;

Correct me if I'm wrong, but if I recorded today's timestamp in a database (2011-12-05 09:00:00) and then looked up that same record in June, I would get 2011-12-05 10:00.. right? Because DST would be in effect in June.

Admittedly, I think I'm making this too complicated, but I just can't seem to figure out a durable solution that doesn't require me changing a configuration file every time we enter/exit DST.
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Ray Paseur
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Regarding this: "if I recorded today's timestamp in a database (2011-12-05 09:00:00) and then looked up that same record in June, I would get 2011-12-05 10:00.. right?"

I expect that you would get back exactly what you put into the database.  PHP and MySQL have different and independent time zone settings.
So, I think I'm starting to understand better.   I just did a test on my Unix server and, sure enough, I got back what I put into the database, even after changing the server time ahead and back one hour.  

Your suggestions were very helpful.  Thank you.
Thanks for the points.  It's a great question, ~Ray