Automated age calculation

Question

How can I calculate my age at compile-time in LaTeX?

Something like:

I'm \myage{day}{month}{year} years old.

would be most awesome.

This could be done using the datenumber package. The number of days would be easy. If you want to get "You are YY years, MM month and DD days old" it is more tricky. See also this somehow related question. — Martin Scharrer, Feb 18 '11 at 16:52

score 23 · Accepted Answer · edited Apr 13 '17 at 12:36

23

You can typeset your age easily using the datetime package and doing some simple calculations.

\documentclass{article}
\usepackage{datenumber,fp}
\begin{document}
\newcounter{dateone}%
\newcounter{datetwo}%

\setmydatenumber{dateone}{1990}{01}{01}%
\setmydatenumber{datetwo}{\the\year}{\the\month}{\the\day}%
\FPsub\result{\thedatetwo}{\thedateone}
\FPdiv\myage{\result}{365.2425}
\myage

\end{document}

You can truncate the figure correctly, i.e., if you 21.6 years old it will give you 21 (see edit), by changing the last line of the code as follows:

\FPround\myage{\myage}{0}\myage\ years old

See also this post.

Edit

Since the rounding of the age elicited a few comments I looked up the legal definition of age (which was probably appropriate in my example). Based on this I have changed the code from FPround to FPtrunc. Thanks to all that made comments. I also changed the days in the year to 365.2425 to increase the accuracy a bit for marginal cases!

edited Apr 13 '17 at 12:36

Community

1

answered Feb 18 '11 at 17:18

yannisl

117,160

5

Most people call themselves 21 years old until their 22nd birthday. So \FPtrunc\myage{\myage}{0} might be more conventional. – Matthew Leingang Feb 18 '11 at 18:10
2

Simon & Garfunkel have a song that goes "I was 21 years when I wrote this song. I'm 22 now but I won't be for long. Time hurries on, and the leaves that are green turn to brown." – Matthew Leingang Feb 18 '11 at 18:11
@Matthew Good point, but given that most people around here are mathematically inclined I will leave the choice up to them. – yannisl Feb 18 '11 at 18:40
Yannis answer with Matthew's addition is exactly what I was looking for. Big thanks for help :) – Suar Feb 18 '11 at 19:06
3

Not to be too pedantic, but the average year has 365.2425 days in it, not 365.25—but I guess it doesn't matter unless you were born before 1900. – Andrew Feb 18 '11 at 22:19
@Yiannis: This is really not a matter of choice. If at all, it's a cultural question, but I don't believe any culture will round. If you're 20.9 years old, you may choose to say "I'll soon be 21 years old", but in the cultures I know of, "I'm 21 years old" would be a lie (in particular in the US if you want to buy alcohol). – Hendrik Vogt Feb 20 '11 at 08:23
1

@Hendrik I know what you mean. Where I grew I had to jump straight from 18.01 to 21 many a times! – yannisl Feb 21 '11 at 17:24
Need to beware of variable names too, Latex doesn't allow names like var1 with numbers in them! – Yan King Yin Jul 01 '15 at 14:21

score 8 · Answer 2 · edited Jan 06 '12 at 16:18

8

The proposed solution does not seem to be completely accurate ; a perhaps more straightforward way of doing this is (replace DDMMYYYY by actual figures)

\usepackage{ifthen}
\newcounter{myage}
\setcounter{myage}{\the\year}
\addtocounter{myage}{-YYYY}
\ifthenelse{\the\month<MM}{\addtocounter{myage}{-1}}{}
\ifthenelse{\the\month=MM}{
  \ifthenelse{\the\day < DD}{\addtocounter{myage}{-1}}{}
}{}

then \themyage{} can be used to show your age.

edited Jan 06 '12 at 16:18

Torbjørn T.

206,688

answered Jan 06 '12 at 16:17

YoungFrog

180

Welcome to TeX.sx! You can highlight code by selecting it and pressing Ctrl + K. – Torbjørn T. Jan 06 '12 at 16:19
Works well and is to the point. I couldn't make the accepted answer work because I need to compute the age before the beginning of the document and got an error. – Shautieh Mar 20 '17 at 07:17

score 3 · Answer 3 · answered Dec 21 '17 at 19:11

I have found that this works very nicely.

%
\catcode`@=11
\newcount\@tempnuma
\def\@null{null}
\def\age#1{\@age#1\@null}
\def\@age#1/#2/#3\@null{%
        \@tempnuma\year
        \advance\@tempnuma by -1900 % Comment this line out for dates of
                                    % the form 2/24/1967 - last 2 digits of yr.
        \advance\@tempnuma by -#3\relax  % gives # of years 
        %\number\@tempnuma
    \ifnum#1 > \month   %anniv month is later in year
            \advance\@tempnuma by -1\relax
    \else
            \ifnum#1 = \month   %anniv month is this month
                \ifnum#2 > \day %anniv day is later in month
                    \advance\@tempnuma by -1\relax
                \fi\relax
            \fi\relax
    \fi\relax
\number\@tempnuma}
\catcode`@=12
%

Usage is: \age{6/25/84} yields the correct age in years, which is what one usually wants. With some twiddling, one could get the months and days.

score 0 · Answer 4 · answered Mar 10 '22 at 17:06

\usepackage{datenumber, fp}

\newcounter{birthday}
\setmydatenumber{birthday}{1995}{09}{06} % my birthday
\setdatetoday
\addtocounter{datenumber}{-\thebirthday} % today - birthday
\setdatebynumber{\thedatenumber} % get date
\FPsub\result{\thedateyear}{\thestartyear} % date year - start year (see datenumber lib doc)
\FPtrunc\myage{\result}{0} %truncate result

I am \myage years old.

Automated age calculation

4 Answers4

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