I started working on December 22, 2023, but my first paycheck was January 4, 2024. Do I have to pay taxes for 2023 or does that fall under 2024? Also, I didn't get a W-2.

I didn't get a W-2 so I figured those last days of December would fall under the 2024 tax year, since the paycheck was on January 4, 2024, but now I've heard conflicting info and am not sure.