Source: Schema.org v30.1 vocabulary. Official byMonth property definition.
What does byMonth mean?
Defines the month(s) of the year on which a recurring [[Event]] takes place. Specified as an [[Integer]] between 1-12. January is 1.
Used on types (domainIncludes)
Expected value types (rangeIncludes)
Schema.org domainIncludes and rangeIncludes are descriptive guidance, not strict validation prohibitions. Check the official reference for updates.
Related reference
Browse all Schema.org types and properties · Google feature support status