I was able to fix it for me by changing the PHx plugin, more exactly the "phx.parser.class.inc.php" file.
I had to change line 270 from:
$output = strftime($modifier_value[$i],0+$output);
$output = strftime($modifier_value[$i],($output + $modx->config['server_offset_time']));
I hope that this helps anyone and I do suggest changing the actual plugin because I think that this is the proper way, or maybe add an option to do this...
May God bless you,
iasmin for Amazing Discoveries