Inspired by Google feature of converting units, such as "20 euro to usd", I tried to ask for "Sat, 1 Jul 2006 14:01:40 -0700 PDT to GMT". Unfortunately, Google don't understand it.
The fallback is to use my Linux:
$ TZ=GMT date -d 'Sat, 1 Jul 2006 14:01:40 -0700 PDT' date: Ð½ÐµÐ²ÐµÑÐ½Ð°Ñ? Ð´Ð°ÑÐ° `Sat, 1 Jul 2006 14:01:40 -0700 PDT'
It is interpreted as a wrong date. I found that it's enough to drop redundancy (timezone shift and timezone name):
$ TZ=GMT date -d 'Sat, 1 Jul 2006 14:01:40 PDT' Ð¡Ð±Ñ ÐÑÐ» 1 21:01:40 GMT 2006
The problem is solved. But I decided to test Google yet again, with the new format. Unfortunately, it haven't helped.