Original: Each period consists of 12 hours numbered 12 (acting as zero), 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11.
Simplified: Both names are from Latin, and numbered from 12, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11.