Is it better to use 0 or NULL as the default for MySQL INT fields that store dates?

Question

I have to live with an INT in our date/time records in MySQL, so I'm trying to figure out whether it's better to use 0 or NULL as the default for those fields. We're migrating, and data is coming in as 0000-00-00 00:00:00, a Unix timestamp, 0, NULL, false, etc, so I'm converting everything through the PHP strtotime() and date() functions, but getting weird results on insert.

Ultimately I can end up with something usable in PHP, but I'm not sure whether after the fact which is better to use as the default in MySQL.

Answer 1

0 is a value. NULL is a lack of a value.

Use NULL.

Answer 2

If you want to express the absence of a value, you should use Null. 0 in epoch time is equal to midnight on January 1, 1970. Therefore, based on the description of your situation I would suggest using Null.

http://www.epochconverter.com/