# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/^[\D]*(?P<from_day>(0?[1-9])|([12][0-9])|3[01])[\.\-\s,■]+(?P<from_month>(0?[1-9])|(1[0-2]))[\.\-\s,■]*(?P<until_day>(0?[1-9])|[12][0-9]|3[01])[\.\-\s,■]+(?P<until_month>(0?[1-9])|1[012])[\D]*$|(?:.*)/\g<from_day>.\g<from_month>-\g<until_day>.\g<until_month>/gm;t' <<< "28.11 16.12
\"13.01 23,09\"
01.08.-31.12
\"01.01,-51.12\"
01.08.-31.12.
01.08.-31.12.
01.01.-31.12.
01.08.-31.12.
01.01.-31.12.
\"01,01.-31,12.\"
01083112
1.02 - 4.3"
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html