Use locale endoding else this generate error in GU : as default time format can have non ascii char on non english locale, but using ascii in locale can generate UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 :
In PyBitmessage/src/bitmessageqt/__init__.py"
l10n.formatTimestamp())
In PyBitmessage/src/l10n.py", line 81, in formatTimestamp
return unicode(timestring, encoding)