slavapestov/factor — pull request #1004 by bjourne (2014-02-22 18:33:18+00:00)
Title: calendar: the incoming timestamps needs to be cloned to keep them from being mutated

Two words in calendar change the gmt-offset instead of creating new tuples. So If you run

now 3 hours >>gmt-offset dup now <=> drop gmt-offset>>

The offset will be 0 when it really should be 3 hours.