unfortunately, it's currently not possible to use UTC (absolute) offsets.
Those relative offsets are all it can do for now.
(and they only adjust the hour, not the displayed day / any date format)Here's a feature request regarding UTC:
#154I might consider to implement it soon though... after the next final release and without the format rewrite I had planned... but I guess one more format shouldn't hurt that much
(and it's taking me way to long to do anything anyway)