Unprecise float evaluation

Hallo Guys,

i am developing an environment system with a realistic sun/moon movement.
To do so i need to implement a function that computes the Julian day.
This is the equation (Sry for German version but the equation is better):

The implementation of this (the last line) is shown in picture one.

Picture two shows the same part with some print messages.

The result of this print is:
2458834.25 + -4.752395 = 2458829.5

The correct result would be:
2458834.25 - 4.752395 = 2458829.497605

The problem i have with that is that the engine rounds the value to only XX.0, XX.25, XX.50 or XX.75.
So every time the value jumps from on case to another my sun/moon does a little jump on the screen too.

Is there a possibility to evaluate the values in a more precise way using blueprints ?