When attempting to acquire imagery (either aerial or satellite), it is important to consider what time of the day or year it was or will be taken.

The time of day is important because of shadows. Depending on the sun's angle to the earth and to the camera, shadows will be visible and could hide necessary detail.

The time of year is important because vegetation will show up best while it is growing/green. Trying to find areas of stressed vegetation in an Arizona June, when most of the vegetation is dried out and dead, could be difficult to do.