Here is a great article on the history of Mărţişor in Romania, for those who are interested.
For those who are not, here is what I can tell you.
It happens on the first of March, which seems to be because of the Roman Calandar, which used to begin in March. It is a really old tradition and you give a Mărţişor to people to wish them strength and health in the coming year. Traditionally, men give the talisman to women, and it is a twisted string of red and white thread to symbolize the passage of winter to spring.
Here is what else I can tell you.
My apartment is once again filled with flowers, and I have some really lovely Mărţişor(s?) from many of my students. It was a good day :)