Just kidding. It's the best time to get your mother flowers. Why flowers? I don't know but mothers really like them. It is a bit suspicious because flowers are pretty, smell good, and hang out with her for periods exceding 20 minutes at once before they come up with an excuse to leave.
Meanwhile she claims to love you, and you do none of those things.
But this is no time to ponder whether your mom is lying when she says she loves you. Instead for this Mother's Day just get her some flowers. It will become a dependency issue so even if she doesn't really love you she'll have to pretend in order to keep her yearly supply of flowers coming.
Hey, and if she is really fiending for some flowers, or you if you just feel guilty about being a terrible kid, you can give her flowers any time. It's not just from Mothers Day you know.