Hi Rohan,
agree with Devendra that this is done by a filter in your aggregate, but suggested filter won't catch all overlap (if overlap is what you are looking for)
An existing record in the database that starts after the newly entered record, and stops before the newly entered record, won't be found with this filter.
this is a filter that will work to catch all overlap :
DB.FromDate < NewRecord.ToDate AND DB.ToDate>NewRecord.FromDate
OR, if a record is not allowed to start on the same day another stops :
DB.FromDate <= NewRecord.ToDate AND DB.ToDate>=NewRecord.FromDate
Dorine