whichth

Whichth planet from the sun is the earth?

And but one argument arose, it was over this abstruse astronomical zodiacal problem: If the first "Jamieson Day" was celebrated in 1898, whichth "Jamieson Day" do we celebrate this year, the thirteenth or the fourteenth? and whichth anniversary is it?

1911, The Druggists Circular: A Practical Journal of Pharmacy and General Business Organ for Druggists, volume 55, The Druggists Circular, page 441

[…] knocking the stuffing out of each other for goodness knows the whichth time this year […]

1975, Tribune, Ceylon News Service, page 4

[…] lay back in the lounger, checking the mantel clock for the he-didn't-know-whichth time. Four-forth-five.

1992, Jan Seale, Airlift: Short Stories, Texas Christian University Press, →ISBN, page 4, →ISBN

But the use of ordinals to answer questions of the form, "The whichᵗʰ member of the ordering?" is as much one of their distinguishing characteristics as the use of cardinals to answer questions of the form "How many?" is one of theirs.

2012, Richard G. Heck, Reading Frege's Grundgesetze, OUP Oxford, →ISBN, page 223, →ISBN