TGraph vertical labels

ROOT
1

Hello All
Im having difficulties rotating the X axis labels on a Tgraph when using SetTimeDisplay

below my code an the output message.
Thnaks for your help

TCanvas *c1= new TCanvas("FactorFits1","plots");
c1->SetGridy(); c1->SetGridx();
TGraph *hFactor1 = new TGraph(VectorCounter1,VectorTime1,VectorFactor1);   
hFactor1->SetTitle("Py ratio");

hFactor1->GetYaxis()->SetTitle("ECAL/Py");
hFactor1->GetXaxis()->SetTimeDisplay(1);
hFactor1->GetXaxis()->SetTimeFormat("%Y\/%m\/%d");
hFactor1->GetXaxis()->LabelsOption("v");

hFactor1->Draw("aP");

The code run fines ,create the plots but dont show vertical labels but a warning

Warning in TAxis::Sort: Cannot sort. No labels

2

Labels’ rotation works only for alpha numeric labels. other labels are rotated automatically when then overlap. you can also plot the time on 2 lines using #splitline