Years
What Second Frost is for
Second Frost keeps the lunar months close to the solar year.
Twelve lunar months do not quite fill a solar year. If the calendar ignored that difference, New Year would move earlier and earlier against the seasons.
Second Frost is the correction. It adds one more winter month when the year needs it, so the next New Year remains near the spring equinox.
This is the same general problem that leap days solve in the civil calendar. The Lilyan solution is lunar rather than monthly arithmetic.
In short
- Second Frost is an extra month.
- It appears before the next spring aligned New Year.
- It keeps the lunar year from drifting away from the seasons.