[tz] Java & Rearguard

Paul Eggert eggert at cs.ucla.edu
Fri May 31 02:08:33 UTC 2019

On 5/30/19 2:14 AM, Stephen Colebourne wrote:
> It is a compatibility requirement of the main Java libraries
> (including icu4j IIUC) that DST is always positive.

Where is this documented? And what do the main Java libraries do in an 
environment where the DST offset is negative? For example, if I run the 
following shell command on a POSIX-compatible host:

TZ='IST-1GMT0,M10.5.0,M3.5.0/1' java [arguments]

can you give an example of what goes wrong and why? This command gives 
Java the rules that Ireland has used since 1996, with Irish Standard 
Time (1 hour ahead of GMT) used in the summer and GMT (a "negative 
daylight saving time") in the winter.

More information about the tz mailing list