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Non native speaker here, it's the second time this week[1] that I see "didn't used to..." instead of what I believe to be the correct form "didn't use to...". Aren't verbs after "did/didn't" always supposed to be in the present tense? For example you would say "I didn't see you last night" rather than "I didn't saw you last night". Is there a grammatical rule I'm missing? [1] the other one was this video by youtuber Vsauce, this video EDIT: wow so many interesting responses, thank you!
