December 18th, 2007
Joda Time
I spent a few hours this weekend converting RubyTime in JRuby to use Joda Time instead of Calendar or Date. That was a very nice experience actually. I’m incredibly impressed by Joda, and overall I think it was worth adding a new dependency to JRuby for this. The API is very nice, and immutability in these classes make things so much easier.
There were a few things I got a bit annoyed at though. First, that Joda is ISO 8601 compliant is a really good thing, but I missed the functionality to tune a few things. Stuff like saying which weekday a week should start on, for the calculation of current week would be very nice. As it is right now, that functionality has to use Calendar. It might be in Joda, but I couldn’t find it.
The other thing I had a problem with – and this actually made me a bit annoyed – was how Joda handles GMT and UTC. Now, it says clearly in the documentation that Joda works with the UTC concept, and that GMT is not exactly the same thing. So why is it this code passes (if assertNotEquals is assumed):
public void testJodaStrangeNess() {
assertEquals(DateTimeZone.UTC, DateTimeZone.forID("UTC"));
assertEquals(DateTimeZone.UTC, DateTimeZone.forID("GMT"));
assertEquals(DateTimeZone.UTC, DateTimeZone.forOffsetHours(0));
assertNotEquals(DateTimeZone.UTC, DateTimeZone.forID("Etc/GMT"));
assertNotEquals(DateTimeZone.forID("GMT"), DateTimeZone.forID("Etc/GMT"));
}
Yeah, you’re reading it right – UTC and GMT is the same time zone. +00:00 is the same as UTC too. But Etc/GMT is not the same as UTC or GMT or +00:00. Isn’t that a bit strange?
