Multiline.pattern: '^\[[0-9]{4}-[0-9]{2}-[0-9]{2}' not working

[Nikhilpawar1985 (Nikhil Pawar)]

I tried different combinations but it not working ..any help
multiline.pattern: ^\[\d{4}-\d{1,2}-\d{1,2}
# multiline.pattern: ^\[[0-9]{4}-[0-9]{2}-[0-9]{2}
# multiline.pattern: '^[\d{4}-\d{2}-\d{2}'