import re
regex = r"(?m)^(\d{2}/\d{2}/\d{4})\n(.*?)(?=\n\d{2}/\d{2}/\d{4}$|\nSome Delimiter|\Z)"
test_str = ("Text Starts\n"
"23/01/2018\n"
"Something here. It was a crazy day.\n"
"Believe me.\n"
"02/02/2018\n"
"Another thing happens.\n"
"Some Delimiter\n"
"20/02/2017\n"
"Text here\n"
"21/02/2017\n"
"Another text.\n"
"Here.\n"
"End Section\n"
"...text continues...")
print(re.findall(regex, test_str, re.DOTALL))
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
[('23/01/2018', 'Something here. It was a crazy day.\nBelieve me.'), ('02/02/2018', 'Another thing happens.'), ('20/02/2017', 'Text here'), ('21/02/2017', 'Another text.\nHere.\nEnd Section\n...text continues...')]