There are so many factors that you can't water by the clock, or the calendar for that matter.
Wind, temperature, ambient humidity, rainfall, tree type, soil, exposure, species, season, container depth & width and construction of the container, size of the tree, amount of moss, etc.
Just be sure to check your trees every day, and water when necessary. The frequency of my watering varies from usually once a day in summer (twice a day on the few days it gets over 105 F) and about once every week in winter. But that is what I have found works for me generally. I am still out there checking every day. Sometimes every other day in winter
Regards,
Matt