Best practice for storing the date in MySQL from PHP

Question

I've been using the unix timestamp all my life.

I like it because it's easy to compare, it's fast because I store it as an integer. And since I'm using PHP, I can get any date/time format with date() function from the unixtimestamp.

Now, some people are saying that it's best to use the DATETIME format. But besides the more suited name, I don't see any advantages.

Is it indeed better to use DATETIME, if so, what are the advantages?

Thanks.

Answer 1

If you store dates as Unix timestamps in the database, you're giving yourself the heavy lifting. You have to convert them to the formats you want to use, you have to do the calculations between date ranges, you have to build the queries to get data in a range. This seems counter-intuitive- surely your "programmer time" is best spent solving real problems?

It seems much better practice to store dates and times in the proper format that MySQL has available, then use the database functions to create the queries for the data you want. The time you would waste doing all the convertions and mucking about is massive compared to the afternoon spent reading (and understanding) 11.6 MySQL Date and Time Functions

Answer 2

I've also been a huge fan of the unix timestamp all my life. But I think the correct answer is: "depends". I recently did a single table database where I wanted to only list URLs. There would be a date field, but the date field is purely for sorting. I.e order by last_crawled. Which means I will never use any built-in date functions on that field. It is merely an easy way to get the oldest entries first and I will never apply date functions to this field. Now, had I made this a date field, I would have lost out on two things:

1. A datetime field is twice the size of an integer
2. Sorting by an integer is faster (not 100% sure of this, pending outcome of this question)

However, for another system I had to store transactional information. This made using internal mysql date functions possible which turned out to be very useful when we had to start doing reports.