Your mother (assuming she is a U.S. citizen) must file Form 709 if she gave you gifts totaling more than $16,000 in 2022.
See https://www.irs.gov/instructions/i709#en_US_2021_publink16784xd0e314
The donee, which is you being the recipient of the gift, does not typically have reporting requirements. However, this will be dependent upon the particular circumstances (such as receiving funds from a foreign bank).
As far as your final question, yes, you could receive up to $16,000 on December 31st and another $16,000 on January 1 without having to file a gift tax return.
