Is it legal for a 19-year-old and 13-year-old to date in Indiana?

No. The legal age of consent is 16 in Indiana. State laws vary as to the degree of charge and punishment, but the 19 year old could face felony rape charges, jail time, fines, and a lifetime "sex offender" label, making it hard to find emloyment and housing. Besides the legal risk, there are serious psychological and emotional risks in involving a child in an adult relationship.