Try `\tikzset{
text field/.style={text height=1.5ex,align=center,rounded corners},
title field/.style={text height=3.14ex,text depth=0em,anchor=south,text
width=5cm,align=center,font=\footnotesize\sffamily},
pics/fillable elective subject/.style={code={%
\node[text field] (-TF)
{\hspace*{-0.5em}\TextField[align=1,name=#1-day,width=1em,charsize=7pt,maxlen=2,bordercolor={1 1 1}]~~/\hspace*{-0.15em}\TextField[align=1,name=#1-month,width=1em,charsize=7pt,maxlen=2,bordercolor={1 1 1}]~~/\hspace*{-0em}\TextField[align=1,name=#1-year,width=2em,charsize=7pt,maxlen=4,bordercolor={1 1 1}]{}~};
text field/.style={text height=1.5ex,align=center,rounded corners},
title field/.style={text height=3.14ex,text depth=0em,anchor=south,text
width=5cm,align=center,font=\footnotesize\sffamily},
pics/fillable elective subject/.style={code={%
\node[text field] (-TF)
{\hspace*{-0.5em}\TextField[align=1,name=#1-day,width=1em,charsize=7pt,maxlen=2,bordercolor={1 1 1}]~~/\hspace*{-0.15em}\TextField[align=1,name=#1-month,width=1em,charsize=7pt,maxlen=2,bordercolor={1 1 1}]~~/\hspace*{-0em}\TextField[align=1,name=#1-year,width=2em,charsize=7pt,maxlen=4,bordercolor={1 1 1}]{}~};