Heaven lies at the feet of the mothers.
And of course, mothers should be appreciated every day not just March 21st. This day certainly has a lot of importance in the Arab world, with extremists decrying the day to be haram and the questionably sane happily spending big on their mamas.
PS It's also the 43rd anniversary of the battle of Karameh, where the feday'een over blew the victory to make up for the state of the low morale the Arab world found itself in after the 6 Day War the previous year.
PPS It's also the new year for Iran. Figure that one out.