No, Beltane is not the first day of spring. It is the midpoint between the spring equinox and the summer solstice - opposite Halloween, which is the midpoint between the autumn equinox and the winter solstice.
Sorry I didn’t make myself clear. In the Celtic clans that celebrated Beltane it was considered the first day of spring...not to be confused with the spring equinox...which they probably celebrated also.