How to get local time zone name from Ruby in the same way as Java does?

Question

I need to find out local machine time zone name from Ruby (from the TZInfo::Timezone.all_identifiers list of values). I need it so that I could set correctly Oracle database session time zone so that I could handle correctly timestamp with time zone values in the database.

I would like to get the same value that in Java you could get with java.util.TimeZone.getDefault().getID() (which on my computer returns "Europe/Riga"). As far as I have had a look on JDK sources there is platform specific C functions which finds this default time zone.

So when using JRuby then I can call this Java method. But I need a solution that I can use with MRI.

I tried to use Time.now.zone but it returns different results (in my case "EET" or "EEST") depending on if currently is daylight saving time or not. So I really would need to get in the previously mentioned location format (like "Europe/Riga") which correctly specifies dates when switching to daylight saving time happens.

Any suggestions?

Answer 1

JRuby returns EET/CDT-like values for compatibility reasons, since C-Ruby does the same. But, since JRuby can easily call the Java layer, you could just call it like tat:

require 'java'
id = java.util.TimeZone.getDefault().getID()

or, in more Ruby-like syntax:

require 'java'
id = java.util.TimeZone.get_default.get_id

Alternatively, you could use JodaTime:

require 'java'
id = org.joda.time.DateTimeZone.getDefault.getID