I can see now that if I comment out the panel size adjustment, I end up with no adjustment at all, thanks.
I think the width is probably sufficient to be able to use the component on a touchscreen, but I'd like to also like to change the height of the buttons and the time spinner, if only for learning purposes.
Using your code as a base and playing around with the height, it seems only the panel increases in height (red arrow), not the buttons themselves:
Is there a second panel that is limiting the height of the buttons? Maybe it's the box filler? How do I find the limiting factor here? Based on how you used panel dimensions of 4 x newWidth (vs 5 x newWidth), it would seem there's one JPanel for the date buttons (green), and then the OK button and the date button JPanel is contained within a parent JPanel (purple)? The output below from a recursive search shows two JPanels, one will be the one we edited, the other could be a parent?
javax.swing.JPanel[,0,658,616x100,invalid,layout=javax.swing.BoxLayout,alignmentX=0.0,alignmentY=0.0,border=,flags=16777217,maximumSize=,minimumSize=,preferredSize=java.awt.Dimension[width=1600,height=100]]
javax.swing.Box$Filler[,0,50,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=,flags=0,maximumSize=java.awt.Dimension[width=32767,height=0],minimumSize=java.awt.Dimension[width=0,height=0],preferredSize=java.awt.Dimension[width=0,height=0]]
javax.swing.JPanel[,0,0,508x100,invalid,layout=javax.swing.BoxLayout,alignmentX=0.0,alignmentY=0.0,border=,flags=16777217,maximumSize=,minimumSize=,preferredSize=java.awt.Dimension[width=622,height=200]]
javax.swing.JButton[,0,34,32x32,invalid,alignmentX=0.0,alignmentY=0.5,border=javax.swing.plaf.synth.SynthBorder@392a6d9d,flags=16777504,maximumSize=,minimumSize=,preferredSize=java.awt.Dimension[width=124,height=100],defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=java.awt.Insets[top=1,left=3,bottom=1,right=3],paintBorder=true,paintFocus=true,pressedIcon=,rolloverEnabled=true,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=<<,defaultCapable=true]
javax.swing.Box$Filler[,32,0,3x100,invalid,alignmentX=0.0,alignmentY=0.0,border=,flags=0,maximumSize=java.awt.Dimension[width=3,height=32767],minimumSize=java.awt.Dimension[width=3,height=0],preferredSize=java.awt.Dimension[width=3,height=0]]
javax.swing.JButton[,35,34,25x32,invalid,alignmentX=0.0,alignmentY=0.5,border=javax.swing.plaf.synth.SynthBorder@2f584bc7,flags=16777504,maximumSize=,minimumSize=,preferredSize=java.awt.Dimension[width=124,height=100],defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=java.awt.Insets[top=1,left=3,bottom=1,right=3],paintBorder=true,paintFocus=true,pressedIcon=,rolloverEnabled=true,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=<,defaultCapable=true]
javax.swing.Box$Filler[,60,0,3x100,invalid,alignmentX=0.0,alignmentY=0.0,border=,flags=0,maximumSize=java.awt.Dimension[width=3,height=32767],minimumSize=java.awt.Dimension[width=3,height=0],preferredSize=java.awt.Dimension[width=3,height=0]]
javax.swing.JButton[,63,34,25x32,invalid,alignmentX=0.0,alignmentY=0.5,border=javax.swing.plaf.synth.SynthBorder@30b1943a,flags=16777504,maximumSize=,minimumSize=,preferredSize=java.awt.Dimension[width=124,height=100],defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=java.awt.Insets[top=1,left=3,bottom=1,right=3],paintBorder=true,paintFocus=true,pressedIcon=,rolloverEnabled=true,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=>,defaultCapable=true]
javax.swing.Box$Filler[,88,0,3x100,invalid,alignmentX=0.0,alignmentY=0.0,border=,flags=0,maximumSize=java.awt.Dimension[width=3,height=32767],minimumSize=java.awt.Dimension[width=3,height=0],preferredSize=java.awt.Dimension[width=3,height=0]]
javax.swing.JButton[,91,34,32x32,invalid,alignmentX=0.0,alignmentY=0.5,border=javax.swing.plaf.synth.SynthBorder@242100ef,flags=16777504,maximumSize=,minimumSize=,preferredSize=java.awt.Dimension[width=124,height=100],defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=java.awt.Insets[top=1,left=3,bottom=1,right=3],paintBorder=true,paintFocus=true,pressedIcon=,rolloverEnabled=true,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=>>,defaultCapable=true]
javax.swing.Box$Filler[,508,0,3x100,invalid,alignmentX=0.0,alignmentY=0.0,border=,flags=0,maximumSize=java.awt.Dimension[width=3,height=32767],minimumSize=java.awt.Dimension[width=3,height=0],preferredSize=java.awt.Dimension[width=3,height=0]]
javax.swing.JButton[,511,34,104x32,invalid,alignmentX=0.0,alignmentY=0.5,border=javax.swing.plaf.synth.SynthBorder@434e257d,flags=16777504,maximumSize=,minimumSize=,preferredSize=java.awt.Dimension[width=124,height=100],defaultIcon=,disabledIcon=,disabledSelectedIcon=,margin=java.awt.Insets[top=1,left=3,bottom=1,right=3],paintBorder=true,paintFocus=true,pressedIcon=,rolloverEnabled=true,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,text=OK,defaultCapable=true]
javax.swing.Box$Filler[,615,50,0x0,invalid,alignmentX=0.0,alignmentY=0.0,border=,flags=0,maximumSize=java.awt.Dimension[width=32767,height=0],minimumSize=java.awt.Dimension[width=0,height=0],preferredSize=java.awt.Dimension[width=0,height=0]]