>I am developing a software for parking lot, where:
>
>time_in is the time the car enters
>timme_out is the time the car goes out
>
>Then I would apply the formula below:
>
>time_out - time_in = minutes_to_pay
>
>I would like your opinions
>
>Can I store time_in in a character field and then
>transform it with val() or can I store date and time into datetime type variable ?

I would use DateTime field/variable. Just keep in mind that the result of time_out - time_in would be in seconds not in minutes.