First day of spring? Isn't that March 22nd? Depends on what calendar you are using.
February 1st is what is known as a cross-quarter day, a day halfway between a solstice and an equinox. In many older European cultures the cross-quarter day of Imbolc marked the first day of spring and still does today in some cultures across the world. The name, Imbolc, I use here coming from the old Gaelic language, one of many names that are used to cover the concept.
This particular year the moment will be at 22:46UT (14:46HST) on the first of February. At that moment the Sun will cross 21h of Right Ascension, exactly halfway between the winter solstice and the spring equinox.
The other cross-quarter days were Beltane, now usually remembered as May Day, the first day of summer. Lughnasadh, the first day of fall, and Samhain, the first day of winter and now celebrated as Halloween or All Saint's day across many western nations. Many of these older pagan celebrations were hijacked by the Christian religion and modified into religious holidays, the celebration of Christmas being the most notable. The other examples of All Saint's Day, Candlemas, St. Brigid's Day, and the Feast of St. John being notable for this adaptation of older pagan holidays.
In agreement with these older traditional definitions I have often noted that the cross-quarter days are more practical seasonal starts than the equinoxes and solstices now marked on most modern calendars. If you consider Samhain the first day of winter the celebration of a midwinter's day on the winter's solstice just matches the seasons, placing midwinter at the darkest time of the year. Likewise Imbloc marks the practical end of true winter in much of the northern hemisphere and the beginning of spring. By the time you reach the spring equinox at the end of April springlike conditions have been evident for many weeks. For my personal calendar this just seems to work better.