1, traverse the date within a given time range

#! /bin/bash start_date=2021.01.01 end_date= 'date -d ""+%s" "end_sec=' date -d ""$end_date"  "+%s"` for((i=start_sec; i<=end_sec; i+=86400)); do day=$(date -d "@$i" "+%Y.%m.%d") echo $day done