$ echo "2023-03-27 08:30:00" > dates.txt
$ echo "2023-04-01 12:00:00" >> dates.txt
$ echo "2023-04-15 18:30:00" >> dates.txt

$ ./target/debug/coreutils date -f dates.txt "+%Y-%m-%d %H:%M:%S"
date: invalid date '2023-03-27 08:30:00'
date: invalid date '2023-04-01 12:00:00'
date: invalid date '2023-04-15 18:30:00'

2023-03-27 08:30:00
2023-04-01 12:00:00
2023-04-15 18:30:00