How did THEN and THAN get mixed up?

How on earth did this particular error get started anyway? It is so jarring to read that such and such is more or less THEN something else. The word is THAN, people.

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THEN refers to TIME -- something happened and THEN something else happened.

Maybe this will help:

RHYME IT:

THEN is about WHEN.

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THAN, on the other hand, is the word for making comparisons -- something is more THAN something else, or less than or better than or worse than, etc.

The internet spreads this kind of mistake like a virus.

Yuck.