nccf_atm_monthly YEAR1 wrong when chunk size 1 month

A simulation started in 19900101 Having 12 chunks (one per month) it calculates ok YEAR1 at all months except december. It gets 1989. https://earth.bsc.es/gitlab/es/atmosphere_diagnostics/blob/master/nccf_atm_monthly.sh#L177 It seems to be fixed removing the -1:

YEAR1=$(( $YEAR0 +(10#$MON0+($jt-1)*$CHUNK_SIZE)/ 12 ))

Experiment: es/Experiments#16