Over the course of September in Dallas, the length of the day is decreasing. From the start to the end of the month, the length of the day decreases by 58 minutes, implying an average daily decrease of 1 minute, 59 seconds, and weekly decrease of 13 minutes, 54 seconds.
The shortest day of the month is September 30, with 11 hours, 52 minutes of daylight and the longest day is September 1, with 12 hours, 50 minutes of daylight.