May be there any tool, but if you want to do it manually you should use some small steps.
1. find the date in sentence.
2. make substring of the sentence as having only date part.
3. because date are in different formats, you should change different find criteria for different date format. You can find by year or by month name or simply use the same date format if possible.
String s1 = "Is there is any holiday on 19-Feb-2012";
int i = s1.IndexOf("Feb")
String date = s1.Substring(i-3, 11);