It’s the old Gaelic calendar. The Druids used to say that Spring began in February. Their logic was that Midsummer was (and is) roughly June 21st and Midwinter was (and is) roughly December 21st meaning that if the year was divided into four seasons, and around June 21st is “midsummer,” then summer starts six weeks before this date, and twelve weeks (a quarter of the year) before this is the beginning of Spring in the first week of February. So astronomical spring starts in February and Meteorological spring starts in March.
As for Brigid, she was originally a Celtic Goddess who was celebrated on Imbolc, which was “Christianised” as the beginning of Spring, usually celebrated about three months after Samhain.
The old Druidic calendar was replaced by the Christian one which also sought to replace our ancient pre Christian gods and goddesses with “more appropriate” Christian festivals. Thus Samhain became All Saints’ Day or “all hallows day,” and the night before became “all hallows eve,” or “Hallowe’en”
The idea that Spring begins in the first week of what is referred to as February (from the ancient Roman “februm” or “to purge” was common amongst pre Christian civilisations and sun worshippers.
It’s more astronomical than meteorological and makes no difference whatsoever to how we record time. The date is movable. This year the Spring Equinox will be on March 20th at 9:24 PM.
By that logic, the ancient Irish would have Calculated that the beginning of Spring would occur approximately six weeks prior to that date which would be roughly February 7th. But the introduction of Christian calendars changed all the original astronomical methods of calculating festivals.
Some useless information which may be of interest during the annual meaningless debate…..