Years of 12 and 13

12 synodic months or 354 whole days { is 11 whole days shorter than 365 }

12 x 29.53 = 354.36 days (354.36 + 10.88 = 365.24)

13 synodic months or 384 whole days { is 19 whole days longer than 365 }

13 x 29.53 = 383.89 days (383.89 - 18.65 = 365.24)

These 2 year lengths of 354 & 384 days are the standard of all Lunar calendars, made up of alternating months of 29 and 30 days. This is due to the necessity to count in whole days, and therefore the average synodic month of 29.53 days is rounded to 29 and 30.

for more info see this page: lunation-matrix

12 month Lunar year (v1)          13 month Lunar year (v1)

alternating months starting with 30 and then 29...

[ 30, 29, 30, 29, 30, 29, 30, 29, 30, 29, 30, 29 ] = 354             [ 30, 29, 30, 29, 30, 29, 30, 29, 30, 29, 30, 29, 30 ] = 384

for more info see this page: 19-year-flower