1. On Friday, I cooked for my mom.
2. Friday, I cooked for my mom.
3. I took a piano lesson om Wednesday.
4. I took a piano lesson Wednesday.
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Are #2 and #4 grammatical without the preposition 'on'?
2. Friday, I cooked for my mom.
3. I took a piano lesson om Wednesday.
4. I took a piano lesson Wednesday.
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Are #2 and #4 grammatical without the preposition 'on'?