Depends on application, really.

Consider setting a timestamp by a user to a server in New York, for an appointment in Sanghai. Now when the user connects in Sanghai, he accesses the same appointment timestamp from a mirrored server in Tokyo. He will see the appointment in Tokyo time, offset from the original New York time.

So for values that represent user time like an appointment or a schedule, datetime is better. It allows the user to control the exact date and time desired, regardless of the server settings. The set time is the set time, not affected by the server’s time zone, the user’s time zone, or by changes in the way daylight savings time is calculated (yes it does change).

On the other hand, for values that represent system time like payment transactions, table modifications or logging, always use timestamps. The system will not be affected by moving the server to another time zone, or when comparing between servers in different timezones.

Timestamps are also lighter on the database and indexed faster.

NOTE: This answer was originally posted at StackOverflow.com by ianaré

I always use DATETIME fields for anything other than row metadata (date created or modified).

As mentioned in the MySQL documentation:

The DATETIME type is used when you need values that contain both date and time information. MySQL retrieves and displays DATETIME values in ‘YYYY-MM-DD HH:MM:SS’ format. The supported range is ‘1000-01-01 00:00:00’ to ‘9999-12-31 23:59:59’.

…

The TIMESTAMP data type has a range of ‘1970-01-01 00:00:01’ UTC to ‘2038-01-09 03:14:07’ UTC. It has varying properties, depending on the MySQL version and the SQL mode the server is running in.

You’re quite likely to hit the lower limit on TIMESTAMPs in general use — e.g. storing birthdate.

NOTE: This answer was originally posted at StackOverflow.com by scronide

From my experiences If you want a date field in which insertion happens only once and u don’t want o have update or any other action on that particular field go with date time .

For example in a user table REGISTRATION DATE filed.

In that user table if u want to know the last logged in time of a particular user go with a filed of timestamp type let that filed updated with a trigger.

NOTE: This answer was originally posted at StackOverflow.com by Kannan Prasad

Not sure if this has been mentioned already, but worth noting in MySQL you can use something along the lines of below when creating your table columns

on update CURRENT_TIMESTAMP

This will update the time each instance you modify a row, sometimes very helpful for stored last edit info. This only works with timestamp, not datetime however.

NOTE: This answer was originally posted at StackOverflow.com by leejmurphy

I always use a UNIX timestamp, simply to maintain sanity when dealing with a lot of datetime info, especially when performing adjustments for timezones, adding/subtracting dates, and the like. When comparing timestamps, this excludes the complicating factors of timezone and allows you to spare resources in your server side processing (Whether it be application code or database queries) in that you make use of light weight arithmetic rather then heavier date-time add/subtract functions.

NOTE: This answer was originally posted at StackOverflow.com by Oliver Holmberg

The main difference is that DATETIME is constant while TIMESTAMP is effected by the time_zone setting.

So it only matters when you have – or may in the future have – synchronized clusters across time zones.

In simpler words: If I have a database in Australia, and take a dump of that database to synchronize/populate a database in America, then the TIMESTAMP would update to reflect the real time of the event in the new time zone, while DATETIME would still reflect the time of the event in the au time zone.

A great example of DATETIME being used where TIMESTAMP should have been used is in Facebook, where their servers are never quite sure what time stuff happened across time zones.

Once I was having a conversation in which the time said I was replying to messages before the message was actually sent.

This of course could also have been caused by bad time zone translation in the messaging software if the times were being posted rather than synchronized.

NOTE: This answer was originally posted at StackOverflow.com by ekerner

I make this decision on a semantic base.

I use a timestamp when I need to record a (more or less) fixed point in time. For example when a record was inserted into the database or when some user action took place.

I use a datetime field when the date/time can be set and changed arbitrarily. For example when a user can save later change appointments.

NOTE: This answer was originally posted at StackOverflow.com by unbeknown

I like UNIX timestamp, because you can convert to numbers and just worry about the number. Plus you add/subtract and get durations etc. Then convert the result to Date in whatever format. This code finds out how much time in minutes passed between a timestamp from a document, and the current time.

$date  = $item['pubdate']; (etc ...)
$unix_now = time();
$result = strtotime($date, $unix_now);  
$unix_diff_min = (($unix_now  - $result) / 60);
$min = round($unix_diff_min);

NOTE: This answer was originally posted at StackOverflow.com by user723220