Solomon divided his kingdom into 12 areas and had 12 individuals overseeing those areas. Then he had each area provide food for him for a month:
Solomon had twelve officers over all Israel, who provided food for the king and his household. Each man had to make provision for one month in the year. (1 Kings 4:7) [ESV]
David had a similar division:
This is the number of the people of Israel, the heads of fathers' houses, the commanders of thousands and hundreds, and their officers who served the king in all matters concerning the divisions that came and went, month after month throughout the year, each division numbering 24,000 (1 Chronicles 27:1)
Chronicles continues by naming the person responsible for the first month, the second month, and so on. As with Solomon's provisioning, there are 12-leaders for 12-months.
These functions seem to follow the 12-month solar calendar not a lunar calendar requires intercalating a 13th every 2-3 years. Are these evidence a solar calendar was in use at the time, at least for these civil matters?