Implementation of the following regular expression using state design pattern in python 3:

(13)?\d\d[- /.](0?[1-9]|1[012])[- /.](0?[1-9]|[12][0-9]|3[01])

Usage Example:

echo "Some text 1397-10-29 blah 1397-10-30 blah" | python3 main.py

Output:

1397-10-29
1397-10-30