Displaying the same date in the web-interface with
different mehtods (timezone +1), I get:

-format----------------------- displayed time -----
plain()                        2006-01-15.21:45:00
field()                        2006-01-15.21:45:00
field(format='%Y-%m-%d %H:%M') 2006-01-15 21:45
pretty('%Y-%m-%d %H:%M')       2006-01-15 20:45

The last line shows that pretty-format is broken (but
not for fields). The journal is correct. It also show
2006-01-15 21:45:00.