The majority of the retailer's stores currently open at 8am and close between 8pm and 10pm.
It has also submitted a series of licensing applications to cover the extended hours ahead of the key Christmas trading period.
Morrisons marketing director Angus Mciver admitted the inconsistency of its opening hours was putting off shoppers.
"Some customers like to shop on their way to work and others after they've put the kids to bed. But one reason they say they don't shop here is they're not sure when we're open," he said.
Morrisons said it would monitor the results of the trial until Christmas and a decision on making the move permanent would follow next year.
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