Due to multiple factors, expect to potentially pay more when booking in March. For low rates, October can be a great choice for travel to Nantes. Flights to Nantes from Sacramento in October are about $1,280 on average during October, but can be found for as low as $653.
Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Sacramento to Nantes as you normally would.