The command \year gives a number instead of text. How is it done?

Question

As I know, in the command sequence \the\year, \year gives a number, and \the converts it to text.

What I don't understand is, how to make a command that results in a number but not a piece of text representing that number, like the command \year?

In other words, if I want \theXXX to generate "1234" (without quotes), what do I replace XXX with?

Answer 1

\year does not just give a number; it gives an internal integer. This is one of the types of integers that TeX knows. Together with the denotation integers (these are just strings of digits, possibly converted between bases) they are known as the normal integers. Besides the normal integers there are also coerced integers, which occur when an internal glue or dimen is coerced to an integer.

TeX goes implicitly from a string of digits to a number, that is, if TeX expects a number then anything that looks like a number is accepted. So 42 is a number. The other way around has to be done explicitly though, either through \romannumeral or \number. When we are dealing with an internal integer, \the is equivalent to \number. Since you ask what you can use for XXXX when you want \theXXXX to print something, the answer is an internal integer. There are quite a lot, the ones that you can easily influence are tokens defined by chardef or mathdef and the contents of count registers.

For non-internal integers you want to use \number instead though. That is to say, \number123 will compile fine, where \the123 will fail.

Answer 2

This question appears to be more about accessing a counter's value than dates. whlt3 has provided some details on that. Here is an example based on What is the proper method of accessing a counter?.

Counters:

You declare a counter with \newcounter{XXX}, set the counters value with \setcounter{XXX}{1234}. Then you can access it as \theXXX, or \the\value{xxxx}, and both produce the same output:

You can change the desired formatting of the counters output via \renewcommand{\theXXX}{\Roman{XXX}}, after which \theXXX results in the counter's value being displayed in roman numerals:

This technique is often used to change the style of chapter/section, etc... numbers. See for example Roman numerals for sections and subsections.

Dates:

If you are interested in specifically formatting and manipulating dates, you should consider

• the datetime package for formatting dates
• the datenumber package for conversion from conversion between dates to numbers

Code:

\documentclass{article}
\newcounter{XXX}
\begin{document}
\setcounter{XXX}{1234}
\textbackslash{}theXXX yields \theXXX\par
\textbackslash{}the\textbackslash{}value yields \the\value{XXX}
\bigskip
\renewcommand{\theXXX}{\Roman{XXX}}
\textbackslash{}theXXX yields \theXXX\par
\textbackslash{}the\textbackslash{}value yields \the\value{XXX}
\end{document}