It seems obvious that you call your mother on her birthday. If your mother is no longer on the planet, or if she is conventionally unreachable (coma, working or vacationing in seriously remote location, whereabouts unknown, you're "dead to her"), thoughts in her direction could soothe–or clear–a heavy soul.
I'm not at all sure that my son, Asa, knows my birthday. Asa is 23, a first year law student. I know Asa loves me every day. I didn't want him to have to realize with a start two or three (or ten) days after my birthday this year that he'd missed it, and feel some pang of guilt or personal disappointment. So I texted him on Sunday and we talked that night (he'd been reading for 7 hours, with 7 ahead of him). Good conversation. Before we hung up, he wished me a happy birthday. (Asa cooks, usually from scratch. Please post recipes suitable for an academically inundated student. I'll make sure he gets them. Thank you.)
[*Listen to Sweet Honey in the Rock sing "On Children" here. Then sing it with them, with me. --T]