St. Valentine’s Day may have been removed from the universal liturgical calendar of the Church (meaning the calendar of dates celebrated by all Catholics throughout the world) but it is still on the liturgical calendar in the sense that it can be celebrated in particular locations (e.g., by a church named for the saint).
The status of the day was probably downgraded because St. Valentine is one of the early Christian martyrs, like St. Christopher, about whom not much is known. When the universal liturgical calendar was reformed after the Second Vatican Council, saints whose historical origins were obscure were removed from the universal liturgical calendar in order to more fully concentrate on the lives of Christ and his Mother. Those saints whose feasts were retained were generally those whose lives historical scholarship could more easily support.
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