In introducing this subject it is necessary to define the keywords kernos and calendar, which are at the core of this paper. The current definition of kernos (plural kernoi) is that it is a pottery ring or stone tray in which several cups for holding offerings are carved. A calendar is a system for managing time whereby which the beginning, the length, and the division of a time period (e.g., 365 days) are fixed, and days and longer divisions of time (weeks, months, and years) are arranged in a definite order. The calendars that have been used by humanity so far are the lunar, the lunisolar, and the solar. In this paper it will be demonstrated for the first time that around 1800 BCE the Minoans used four stone kernoi as solar calendars which counted the 365 days as follows: three days for celebrations (at the beginning of the year) + five months (of thirty-six days per month) + two days for celebrations (at the middle of the year) + five months (of 36 days per month). The kernos of fig. 1, unearthed by Evans at Knossos, was used as a one-year solar calendar. Later, in about 1550 BCE, the Minoans improved this one-year solar calendar by including one leap year every 4 years, as is demonstrated by a second artifact, also unearthed by Evans at Knossos, which has been partly decoded by Gregoriades and is further explained in this paper.