pg_dump and timestamp : problem with TimeZone

I have some columns with timestamp data type wich includes the time zone.
I access these columns using JDBC which handle the time zone automaticly.
Writing and reading data work fine.

Though when I dump the base and restore it, the date are 2 hours later. Is
seems to me that the timezone is lost somewhere.

Here are technical information :
- I've launched my base (7.1.3 with cygwin) while TZ=GMT-2.
- To dump I use : pg_dump.exe -c -F c -Z 9 myDB
- To restore I use : zcat file.gz | pg_restore -v -c -F c -d myDB

For both dump and restore TZ is GMT-2.

Thanks for your hints...

Emmanuel Guyot