Grammar

Have to + Verb

Use have to  to express necessity. Use don't / doesn't have to  to express lack of necessity.

For the present or future 

Affirmative                                              

I have to go to the dentist today.

I have to do the laundry tomorrow.

He/She has to clean the kitchen.

For the Past

I had to go to the dentist yesterday.

For the Present or Future

Negative

I don't have to go to the dentist today.

I don't have to do the laundry tomorrow.

He/She doesn't have to clean the kitchen.

For the Past

I didn't have to go to the dentist yesterday.