How to make "old-style" the default for numerals?

Question

I want to be able to use the \oldstylenums{} command as a default way for display my numbers, but only outside of math mode. Is this possible to do? I know some fonts come with this numbering system, but is there a way to make the old style the default way for displaying numbers in, let's say, the default font?

Thanks greatly!

Edit: MNW

\documentclass[a4paper,12pt]{extarticle}

\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{graphicx}
\usepackage[colorinlistoftodos]{todonotes}
\usepackage[a4paper,margin=1.5in]{geometry}
\begin{document}
This is a document in the default font, made on 12/3/2014. The numbers in this document need to be in the Old English style (where the number's height differs from each other).
$$\text{This is a math block. These numbers should display as modern English style:}12/3/2014}$$
\end{document}

Answer 1

This uses Latin Modern which is a revised version of Computer Modern.

\documentclass[a4paper,12pt]{extarticle}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{cfr-lm}
\begin{document}
This is a document in the default font, made on 12/3/2014. The numbers in this document need to be in the oldstyle figures, which means that some numerals drop below the baseline.
\[\text{This is a math block. Lining numbers:}12/3/2014\]

{\lstyle To temporarily switch to lining figures, you can use \verb|\lstyle| which will produce 0123456789.
  \tstyle To temporarily switch to tabular figures, you can use \verb|\tstyle| which will produce 0123456789 if lining figures are active or \ostyle 0123456789 if oldstyle are being used.}

{\plstyle\verb|\plstyle| explicitly requests proportional, lining figures such as 0123456789}. {\tlstyle\verb|\tlstyle| explicitly requests tabular, lining figures such as 0123456789.} {\postyle\verb|\postyle| explicitly requests proportional, oldstyle figures such as 0123456789} and {\tostyle\verb|\tostyle| explicitly requests tabular, oldstyle figures such as 0123456789.}

Alternatively, commands such as \verb|\textpl{}| will typeset their argument using the relevant style:
\begin{quote}
  \textpo{0123456789} \verb|\textpo{0123456789}|

  \textto{0123456789} \verb|\textto{0123456789}|

  \textpl{0123456789} \verb|\textpl{0123456789}|

  \texttl{0123456789} \verb|\texttl{0123456789}|
\end{quote}

\end{document}

Note that, as Mico points out, this has nothing to do with Old English which is a historical ancestor of contemporary English, used long, long before figures were typeset in any style at all! Usually, these figures are called oldstyle (OSF) or sometimes just text or hanging, while the more modern-looking ones are described as lining.

Oldstyle figures are usually, but not necessarily, also proportional i.e. a figure '1' has a smaller width than a figure '8', for example. In contrast, tabular figures have equal widths. Latin Modern actually provides oldstyle tabular and lining proportional figures, as well as oldstyle proportional and lining tabular. This is worth bearing in mind as it affects the options for cfr-lm and the effect of font commands which switch between styles.

For example:

\usepackage[rm={lining,proportional},sf={lining,proportional},tt={lining,proportional,variable}]{cfr-lm}

will use lining, proportional figures as default - not lining tabular.