In the center of the zodiac there is the sun in a form of a youth riding a chariot drawn by four horses. I suggest that the existence of the sun in the center is an indication that this is a solar calendar. The zodiac at Beth Alpha is not compatible with the Jewish zodiac. In the four corners of the square enclosing the cycle of the Zodiac are shown the four seasons of the year. It is hard to understand the reason why the craftsmen did not show the seasons near their corresponding months.
Spring is found near the summer months, Summer near the autumn months, and so on.
We find the same in the Na'aran mosaic. There the symbol of Spring is shown near the Zodiac signs Libra and Virgo, and Autumn opposite Aries and Pisces, and so on. I would imagine that he was given instructions as of what to do and at least some members of the community were following his work. A project of such magnitude takes at least some months to accomplish and this gives plenty of opportunities for everybody to notice mistakes. In short, the zodiac was intentionally constructed in this manner.