This is a bastardization of a phrase.
Problem:
The second “in” is incorrect in this phrase.
Explanation:
The conjunction “and” is often mispronounced by Americans as if it were the preposition “in”.
The correct phrase is “in this day and age” — with the conjunction “and” between the word “day” and the word “age” — because one can write “in this day” or “in this age”.
For fun, I searched Google for each of the following (with the quotation marks, to avoid variations) and got about the indicated numbers of matches:
- “in this day and age” — with the conjunction “and” — 3,030,000 matches
- “in this day in age” — with the preposition “in” — 113,000 matches
This tells me that Web authors have used the correct “in this day and age” versus the incorrect “in this day in age” by a ratio of 26.8-to-1, which is very good.
Solution:
“in this day and age”