Or you're in any timezone significantly ahead of the US (so like over 40% of the world's population). It's already 11.35pm here in India, and most moms (and reasonable adults) are already asleep. China/SE Asia/Jp etc are even further ahead.
That's how the date is determined, it's the third Sunday of Lent, "mothering sunday". Hence why the date changes every year (as the dates of Lent move because Easter Sunday is the first Sunday after the first full moon after the Equinox).
Yes, it pre-dates the gift card (and gift) industry. I seem to recall being told it was to allow servants to go home to see their mothers. See how vaguely I framed that.
It’s the 31st of May