The word “and” creates a plural here in English – you’re talking about more than one century, after all.
Dutch adopts a different mindset in such cases: 19th century is singular, 20th century is singular, so it’s negentiende en twintigste eeuw. Here are some examples from real life:
- 19th and 20th century => should be centuries
- class IIb and III => should be classes
- in the metaphorical and literal sense => should be senses
- found in the Service Calls and Workflow module => should be modules
- (Op Frankrijk en Zweden na) With the exception of France and Sweden => should be exceptions
Note that there isn’t necessarily a grammatical error here. There could be a single module handling those two functions and that is how the English native speaker is likely to read it!
While we’re talking about centuries, a reminder that the ordinal number gets hyphenated on when the phrase is used as an adjective: an eighteenth-century drawing room, a twentieth-century invention. But that use of the hyphen will be another post later!
Prevalence: moderate. There are various issues with the use of plurals in Dutch and English that aren’t always easy to keep separate and classify, so it’s not easy to be categorical.
Frequency: medium-high. Liable to occur more than once in a text.
Native: no. This one seems to come from a Dutch mindset.