Creating an index for birthdays

Question

I feel like I should be able to figure this out but after poking around for hours at a time over several months, I'm at a loss. Essentially I want to do something like the following:

\documentclass{article}
\usepackage{imakeidx}

\newcommand{\bday}[3]{\index{#1!#2!#3}}

\makeindex
\begin{document}

\section{Birthday people}
Ted's birthday is March 20.\bday{March}{20}{Ted}\\
Bob's birthday is March 20.\bday{March}{20}{Bob}\\
Ann's birthday is April 30.\bday{April}{30}{Alice}\\
\printindex

\end{document}

And yet have the output of the index look like this, where they are sorted into headings (months, in calendar order rather than alphabetical) and combined by dates, and without page numbers:

Is there a reasonably straight-forward way to do this? Thanks.

Answer 1

Here is something that gets you started:

I used xstring to specify the sort order for the months. One can write a case statement without this pacakge if so desired.

To combine the items into a single line, use a semi-colon as the separator and eliminate the page number, I redfined \subsubitem.

\def\subsubitem#1,#2{#1;}

A less hackish method to eliminate the page number is given in Remove page number from index entries, but I was not able to ge that to work at this time. I know I have used that solution in the past so not sure why it is not working currently.

Code:

\documentclass{article}
\usepackage{imakeidx}
\usepackage{xstring}

\def\subsubitem#1,#2{#1;}% Combine into one line
\newcommand{\bday}[3]{%
    \IfStrEqCase{#1}{%
        {January}{\index{01@#1!#2!#3}}%
        {Feburary}{\index{02@#1!#2!#3}}%
        {March}{\index{03@#1!#2!#3}}%
        {April}{\index{04@#1!#2!#3}}%
        {March}{\index{05@#1!#2!#3}}%
        {June}{\index{06@#1!#2!#3}}%
        {July}{\index{07@#1!#2!#3}}%
        {August}{\index{08@#1!#2!#3}}%
        {September}{\index{09@#1!#2!#3}}%
        {October}{\index{10@#1!#2!#3}}%
        {November}{\index{11@#1!#2!#3}}%
        {December}{\index{12@#1!#2!#3}}%
    }%
}

\makeindex
\begin{document}

\section{Birthday people}
Ted's birthday is March 20.\bday{March}{20}{Ted}
Bob's birthday is March 20.\bday{March}{20}{Bob}
Ann's birthday is April 30.\bday{April}{30}{Alice}
\printindex

\end{document}

Answer 2

Thanks to @Peter above, I was able to get something working. I abandoned trying to include the month in the index and just built twelve separate indices. Not elegant but much more easily formatted and controlled. Essentially the following code and then format the chapter or section headers for the indices titles.

\documentclass{article}
\usepackage{imakeidx}

\def\subitem#1,#2{\, #1;}% Combine into one line
\newcommand{\bday}[3]{\index[#1]{#2!#3}}

\makeindex[name=January,title=January,columns=1]
\makeindex[name=February,title=February,columns=1]
\makeindex[name=March,title=March,columns=1]
\makeindex[name=April,title=April,columns=1]
\makeindex[name=May,title=May,columns=1]
\makeindex[name=June,title=June,columns=1]
\makeindex[name=July,title=July,columns=1]
\makeindex[name=August,title=August,columns=1]
\makeindex[name=September,title=September,columns=1]
\makeindex[name=October,title=October,columns=1]
\makeindex[name=November,title=November,columns=1]
\makeindex[name=December,title=December,columns=1]

\begin{document}

\section{Birthday people}
Ted's birthday is March 20.\bday{March}{20}{Ted}
Bob's birthday is March 20.\bday{March}{20}{Bob}
Ann's birthday is April 30.\bday{April}{30}{Alice}

\printindex[January]
\printindex[February]
\printindex[March]
\printindex[April]
\printindex[May]
\printindex[June]
\printindex[July]
\printindex[August]
\printindex[September]
\printindex[October]
\printindex[November]
\printindex[December]

\end{document}