It's often found on Wikipedia in the titles of articles, and here on this site:

1916

In the example above (if it doesn't render correctly, say you're on mobile, see image below), the 9's tail goes below, and the 6's head goes above.

What is it called (I wasn't able to find out), and is there a historic reason behind this style?

Solution 1:

According to Fonts.com,

Oldstyle Figures:

Oldstyle figures (also known as non-lining, lowercase, hanging, or text figures) have varying heights and alignments, as opposed to lining figures, which are of uniform height and alignment. Oldstyle figures are similar to lowercase characters in that they share the same x-height and have ascenders (the 6 and 8) and descenders (the 3, 4, 5, 7 and 9).

See also Typography Deconstructed:
Old-Style Figures:

Style of Arabic Numerals where the characters appear at different positions and heights as opposed to the modern style of all numerals at the same size and position are called Old Style Figures. Some Old Style figures sit entirely above the baseline while others (such as the tail on the numeral 9) descend below the baseline. Often Old Style Figures are available only in Expert Character Sets although some fonts may come with both Old Style Figures and Lining Figures (those that sit on the baseline). Also Known As: ornamental figures, old style numerals, non-lining

And Wikipedia:
Text Figures:

Text figures (also known as non-lining, lowercase, old style, ranging, hanging, medieval, billing, or antique figures or numerals) are numerals typeset with varying heights in a fashion that resembles a typical line of running text, hence the name.Georgia is an example of a popular typeface that employs text figures by default.
Remember to also see the Design and History sections for more details.

HTH.