The notation  hydrated compound ânH2O , where n is the number of water molecules per formula unit of the salt, is commonly used to show that a salt is hydrated. The n is usually a low integer, though it is possible for fractional values to occur. For example, in a monohydrate n is one, and in a hexahydrate n is 6.
When does spring start? How you define the first day of spring depends on whether you follow the astronomical or meteorological seasons. This year, spring will take place between March 20 and June 21, if you use the astronomical method. But it starts slightly earlier, between March 1 and May 31, if you follow the meteorological calendar.
I am sorry but your contention that the first day of spring is the equinox, the first day of summer the solstice, etc., simply is not true. The so called beginning of summer (the summer solstice around June 21st) and the end (the equinox around Sept 21 or 22) is merely the astronomical beginning and end of summer, nothing more nothing less.