Refer to the lease agreement, specifically to any cancellation clause.
If the lease agreement is month-by-month, then a calendar months notice is required to cancel the lease.
If the lease agreement is for a fixed period and there is no cancellation clause, then the tenant can rely his right to early cancellation in terms of the Consumer Protection Act but remember the landlord can charge a reasonable cancellation penalty.
Refer to: CPA Can the tenant cancel the lease early (see wiki article)