The regular expression does not match the string as the last separator is a full stop and no colon.
Please note that the field YEAR is a 4-digit number according to the ID3 standard.
To keep a more detailed date, try RELEASETIME
Thank you for the response. I have no knowledge of expressions, I was using Google to find the expressions and trying them out. This one seems to be mentioned at more than one places so I assumed this to be correct.
Could you help me with what would be the correct expression ?