You can use "I heard you had..." about something that happened in the past:

> I heard you had an accident last week

> I heard you had got married

Or about something in the future that may not go ahead or has already been cancelled

> I heard you had a date next week with that cute guy from accounts...

> I heard you had a job interview next week but it fell through

If you are talking about something in the future that will definitely go ahead, you should really use 

> I heard you **have** a job interview next week

> I heard you **have** Diwali next week, will you celebrate?