/\b\d{1,2} de [a-z]+ (de 1\d{3}|del 2\d{3})/i
説明:
\b ... requires a word boundary, since the following character is a digit
(and thus a word character) this will only match if the date is
preceded by a character that is not a letter, not a digit and
not an underscore
\d{1,2} ... one or two digits
de ... literally "de"
[a-z]+ ... any letter from a-z, at least once but an arbitrary number of times
(de 1\d{3} ... literally "de" followed by "1" and 3 more digits
| ... or
del 2\d{3}) ... literally "del" followed by "2" and 3 more digits
i ... make the whole thing case-insensitive (you can omit this if needed)
また、正規表現内のすべてのスペースは、他の文字と同様に扱われることに注意してください。
または、代わりに、[a-z]+
次のような有効な月のリストを指定できます
/\b\d{1,2} de (...|septiembre|...) (de 1\d{3}|del 2\d{3})/i
(... をさらに月の名前に置き換えて、|
それらを区切ってください)