How-To: Get human-friendly dates in Java using the Calendar class

ISO-8601 has a PosseAs part of the groundwork for some upcoming Java shenanigans I’ve finished off reading/skimming Head First Java – and it’s a truly excellent book. I wish it covered Connector/J & MySQL, but I can find that knowledge elsewhere so it’s not that big of a deal.

As part of today’s prep I ended up writing something I didn’t think I’d have to – a function to get a nice, human-readable date as a String. I don’t like having to write things like this because surely getting a nice, human-readable version of what’s essentially a timestamp (if the Date class wasn’t deprecated) has been solved. By which I mean that it’s done – let’s never, ever solve that same problem again. But the issue is that if you don’t know where to look for the solution, then it can take you longer to find it than to solve the problem again, and I think that’s what’s happened to me today when I didn’t feel like learning and using the joda-time API to do something I felt core Java should be capable of.

Before we get to the source code I’d just like to direct a quick word to to the Java API Calendar class developers to say:

  • I don’t care who you worship – the first day of the week is Monday, please see ISO-8601, and
  • Chopping and changing between zero-based constants and one-based constants sucks massive d*cks.

Anyways, the getFriendlyDate function gets a day/month/year from a Calendar object and converts it into something a human being might like to read, like this…

And the source code to perform this scandalous transformation is:

Update 13-Oct-2011: Just realised that the 1st, 2nd, 3rd etc. stuff is broken because I’m checking the last digit in the day of month and using that, so if it ends with 3 I give the suffix “rd” making it “3rd”, which is fine until you get to the 13th, which comes out as “13rd”… I don’t have time to fix it up right now, but I will in the near future. Or do a total re-write using the mighty Shetboy’s formatting advice (see comments).


How to: Create and insert SQL DATE or DATETIME objects using PHP

I was helping a student with a bit of project work the other day and had to create a properly formatted Date object from input provided by some dropdown menus, so in the spirit of only ever solving the same problem once, this is how you go about it… I’ll use MySQL for this example, but if the DATEs or DATETIMEs or whatever you’re using have a slightly different format in your DBMS of choice, then the principle’s the same to generate a compatible object.

MySQL Time Formats

The MySQL DATE type has the format YYYY-MM-DD, so for example today (or at least when I’m writing this post) would be 2011-08-19.

The MySQL DATETIME type has the format YYYY-MM-DD HH:ii:SS, so if it’s 9:36am and 53 seconds into the 19th of August 2011, that would be 2011-08-19 09:36:53.

The formatting of the numbers (i.e. the sequence of digits) is super important, but the dashes and colons are optional. This means that when you’re creating a PHP object to represent a DATE or DATETIME, you could create an object which contains 2011-08-19 or 20110819 etc. and MySQL would accept them as the exact same thing.

Constructing a suitable object in PHP

To create our PHP object, we’re going to use the PHP date and mktime functions. For this example I’m just going to create some variables which hold any date or time values, but in the real world you’d probably get them from a dropdown menu or calendar control.

Which when we then take a look at the database shows us:

DateTime Database Record


Automatically padding out numerical data with leading zeroes

If you need to work directly with numerical data (as opposed to strings), then you can use the following function (written by matrebatre over on the str_pad page) to pad out your data:

Done & dusted.