No. Four of them (the solstices and equinoxes) always vary because they are linked to the movements of the sun and moon, but are generally around the 21st. The others used to move but depending on the branch of paganism may be fixed to particular dates.
Imbolc (or Candlemas) - 1st/2nd February
Ostara - Spring Equinox - 20th/21st March
Beltane (or May Day) April 30th/2nd May
Litha - Summer Solstice - 20th/22nd June
Lammas/Lugnasadh - 1st/2nd August
Mabon - Autumn Equinox - 20th/21st September
Samhain (or Halloween) is 31st Oct/1st November but most people would obviously go for 31st Oct
Yule - Winter Solstice - 20th/22nd December
Of course, some of those are turned completely upside down if in the southern hemisphere.