use timestamps or date ?

[toxic_brain]

i am developing a shopping cart portal which users can upload produnct details and list in the site..

i need a lot of date calculations like adding 7 days to a date, find differences between two dates in days etc..

what type of database field should i use?

timestamp type or datetime type?

pls suggest...

[Oersoep]

If you do the date calculations in php it doens't matter:

SELECT UNIX_TIMESTAMP( dbfield ) as utime FROM whereever

$time = strtotime( "+7 days", $row['utime'] );

If you use date you'll just dump the hours and minutes and seconds I guess, so your timestamp will be a multitude of 246060. I don't believe it'll give you trouble.

You can also do the date ajustments in MySQL:

SELECT unix_timestamp( dbfield + INTERVAL 7 DAY ) as utime FROM sometable

In some versions timestamp has an auto-update behaviour. The first timestamp in the table updates when you update the row. 4.1 doesn't do it anymore I think.
You'd better keep an eye on that before you get weird bugs.

Check out this page:
http://dev.mysql.com/doc/mysql/en/date-and-time-types.html

[toxic_brain]

thanx..