Morrisons supermarket in Ascot Road, Watford, is to open for two hours extra each day.
From this week the store has opened at 7am and traded through until 11pm, instead of 8am until 10pm, to meet the demand of shoppers.
Latest research shows one in five now regularly shop outside of "normal" week day hours. They visit a store between 6am and 9am or after 8pm at night.
Half of early morning and late evening shoppers say they prefer these "quieter" times, 37 per cent claim it better suits their working hours, and one in 20 say they want to put children to bed before heading to a supermarket.