proper noun
San Solterín is masculine in Spanish.
Singles' Day, Singles Awareness Day
“El 13 de febrero es San Solterín, una jornada en la que las personas sin pareja reivindican la soltería.” — February 13 is Singles’ Day, a day in which people without a partner claim singleness.
From San Valentín, changing Valentín by soltero (“single”) + -ín.