For those churches that follow a liturgical calendar, Pentecost Sunday falls 50 days after Easter -- this year on May 15. Ascension Day, 10 days prior, fell on May 5, though some churches will mark it on Sunday, May 8, rather than have a special service on Thursday. Of course, a large percentage of churches don't follow such a calendar and won't mark those days at all.
That is fine, as I confess that I have never marked these days myself. However, it seems curious that churches that don't find a need to mark these biblical events will nonetheless observe a purely secular holiday, Mother's Day, on this Sunday.
Again, I can understand the belief that anniversaries of biblical events don't require marking. However, ignoring the church calendar while observing a non Christian one seems to be a strange choice.