\documentclass{article}

\usepackage{polyglossia}
\setmainlanguage{welsh}
\setotherlanguage[variant=british,ordinalmonthday=false]{english}
\usepackage{xinttools}
\usepackage{longtable}

\begin{document}

\month=8
\year=2015
\begin{longtable}{lll}
\xintFor* #1 in {\xintSeq{7}{9}}\do
  {\xintFor* ##1 in {\xintSeq{1}{31}}\do
    {\day=##1\month=#1\relax\today & \day=##1\month=#1\relax\formaltoday & \day=##1\month=#1\relax\textenglish{\today} \\ }}

\end{longtable}

\end{document}