The "tides" we talk about in the Grand Canyon are not the natural tides you may be used to if you live near a coast. Natural tides are caused the gravitational effects of the moon and sun. The "tides" in the Grand Canyon are caused my variations in the release from the Glen Canyon dam. Because these releases are man-made, they can occur at any time. Fortunately, they tend to tend to occur at a regular schedule. But be aware, that the schedule could change.
The amount of the tide also varies. The dam is used to generate electricity, so when the more electricity is needed (typically the summer months) by the public, more water is released to generate it.
Water is released constantly by the dam; its the rate that changes. When the rate goes up, a pulse is generated at the dam and moves down the river. Time time it takes the pulse to move downstream from dam is the cause of the different time of high-tide at different places along the river.