Guido,
While all the units of time are done in seconds internally, you can work around this in SystemModeler.
In this model I have a filter that has a one year time constant (talk about moving slowly!). I want to plot it in years, not seconds:
![enter image description here](http://community.wolfram.com//c/portal/getImageAttachment?filename=ScreenShot2018-09-14at9.39.37AM.png&userId=599067)
Note that the step starts after one year (which I entered in days in the dialog (display units) but it shows up as seconds on the built-in block. I made my own seconds to year converter block:
model ToYear
extends Modelica.Blocks.Interfaces.SISO;
equation
y = u / (3600 * 24 * 365);
annotation(Diagram(coordinateSystem(extent = {{-150, -90}, {150, 90}}, preserveAspectRatio = true, initialScale = 0.1, grid = {5, 5}), graphics = {Text(visible = true, origin = {-135.776, 24.908}, extent = {{-30.776, -3.301}, {30.776, 3.301}}, textString = "Seconds"), Text(visible = true, origin = {118.717, 25}, extent = {{-11.283, -5}, {11.283, 5}}, textString = "Years")}), Icon(coordinateSystem(extent = {{-100, -100}, {100, 100}}, preserveAspectRatio = true, initialScale = 0.1, grid = {10, 10}), graphics = {Rectangle(visible = true, lineColor = {0, 114, 195}, fillColor = {255, 255, 255}, extent = {{-100, -100}, {100, 100}}, radius = 25), Text(visible = true, textColor = {64, 64, 64}, extent = {{-150, 110}, {150, 150}}, textString = "%name"), Text(visible = true, origin = {-147.2, 47.902}, extent = {{-45.346, -12.098}, {45.346, 12.098}}, textString = "Seconds"), Text(visible = true, origin = {140, 45}, extent = {{-33.849, -15}, {33.849, 15}}, textString = "Years")}));
end ToYear;
Now in the Simulation Center do an X-Y plot of toYear1.y vs filter.y
to get
![enter image description here](http://community.wolfram.com//c/portal/getImageAttachment?filename=ScreenShot2018-09-14at9.58.41AM.png&userId=599067)
All other units (other than the time base) can be dealt with by using displayunits and doing conversion to your desired unit in Simulation Center. I know you posted about using operator records but I do not see how that will help you in this case (unless I am missing something)
Is this what you were looking for?
Regards,
Neil