Find primary current in 3 phase transformer
WYE to DELTA or DELTA to WYE results in positive or + 30 deg shift.
where a leads b leading c 


  Yes it matters how it is wired. There is never any phase displacement or shift between two common windings, but there MAY be a phase displacement or shift between the line voltages of two transformers depending on how the windings are connected.


In this example B+ goes to A' or A'-B  or C'-A
Yd11  with 30 deg lead. (secondary leads primary by 30 deg.) and primary WYE lags secondary DELTA   

 

Why does math use CCW for positive angles and clocks rotate the opposite direction?

... because in math everyone uses Archimedes and Cartesian standards with right axis as + and vertical axis at top is +ve  ( same in schematics for V+ to top)
 

Rotating a circle past any reference point in the orientation as you are told (CCW is positive) then Delta to WYE or WYE to DELTA if in same sequence given  results in 30 rotation to left or CCW or POSITIVE 30 deg.  

Positive angles in Trigonometry   oppose direction of clock. It does not mean we go backward in time.  The cicle rotation std is also show here as CCW for positive degrees when rotating the circle past any reference point.



See again for b to lag a the triangle must be rotated CCW for POSITIVE ANGLES with positive time. \$\phi=\omega t\$